I have been given a ferret by someone who said he kept him on his allotment. I could use some help on stopping him biting, please

Hmm there are several methods to deal with biting.  TEll us why/when he bites.  Also, if you could tell how long you've had him and how old he is, it may help.

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I have only had Zane for three days, i know its a big change for him and he has to get used to things i just want to do things right from the beginning if you see what i mean.
I was given Zane by a man who said he kept him on his allotment and fed him cat food so im guessing he didnt get a lot of human interaction.

I dont know how old he is as the guy who gave him to me didnt know, but he seems small and very slim. I bought him a ferret harness so he can go and play i the garden but even on its smallest setting he can slide out.

He doesn't bite all the time, he lets me pick him up but when i try to stroke him he tries to bite my hand. If he cant reach that hand he sometimes tries to wriggle to bite the hand thats holding him.
He hasnt drawn blood i just have a lot of little scratches from his teeth.
If he bites he gets a grip and holds on.
I googled ferret biting and so far nothing has even made him let go. If i scruff him he holds on, if i tap his nose he holds on a little tighter, if i tell him no in a firm voice he just looks at me while he holds on.
He only lets go when his teeth slide off the lump of skin as i hold him scruffed.
When he feels hes grip slipping he tries to get hold of me with his feet to pull me closer to re bite me.

When he is out of the cage he runs around making the happy ferret noise and has to come and see what you are doing. He tries to climb your legs and seems to want attention, i pick him up but when he tries to bite i tell him no put him down and ignore him for a little bit.

He really is very sweet and i want to be able to play with him and fuss him without him latching on to my hand.

It actually sounds like you're doing ok.  He ppobably wasn't nip trained before and it doesn't sound like you're describing serious biting.  Time out is a good strategy for a nipper, but I let them get away with nipping as long as it does't turn into biting, because sometimes it's like a sign of affection.  I think that Pandora nips instead of kisses.  She will lick our arms when being held, but has never offered a a real kiss.

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The first night I had him I managed to hold him still for a little bit and stroke his head till he fell asleep,  but then he was back to biting. 
I would say it was biting instead if nipping because he gets a good lump of skin and holds on till I get him off which is no easy task. 
I know ferret skin is tougher then ours so he make think he's being playful I just need to teach him how to play without causing pain,  because it really does hurt. 
This morning we were at the stage where apart from picking him up which you can do if your quick and hold him in such a way that he can't reach your hand,  he was biting or attempting to as soon as he was in reach.
How do I teach him to stop biting when I haven't even found a way of getting him to let go? 

two methods are time out for 3 minutes or scruff/drag, each with a NO BITE command.  scruff drag meand grip by the scruff of the neck and drag a few feet on the floor to establish that you are dominant.  Be consistant in your method.  It shouldn't take long to learn

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When I nip trained my ferret I used bitter apple spray (biting deterrent for ferrets) on my hands. Then if he nipped I would say ouch or some kind of other sound. It sounds like he does want human company though. It will probably just take a little time. Also, you can reward him by letting him lick a ferret vitamin or furotone while you hold him, so he can associate you holding him with something positive. And you could give him a little treat and praise him after he's let you hold him a while without biting. These are things I tried when I got my ferret off of a man who hadn't held him a lot. It worked for him, but he was only 4mnts old. I think it could work with an older ferret too.

Thank you for all the advice.
Today when i came home i let him out and he sniffed around for a min then tried to climb my jeans, over and over again, climbing on things to try and reach higher.
When i picked him up he went straight to trying to bite me.
I am doing the time outs and dragging him across the floor while scruffed..so far it seems to really piss him off and the min i let him go hes straight back trying to climb my legs.
Yesterday he got hold of my finger but with his canines in  front of my finger so it didnt really hurt when he tried to drag me under the wardrobe lol, he still ended up in a time out.
When he tries to bite me and fails i say no biting in a firm voice and  you can see on his little ferret face he knows what you mean, then he tries again.
Now i'm sitting next to his cage listening to music and telling him he's a good boy when hes calm, as i'm guessing he hasn't spent a lot of time with people.
Can anybody suggest and good, healthy ferret treats that i can reward good behaviour with?

healthy ferret treats that i can reward good behaviour with?

How about some baby food.  Gerber chicken broth... no veggies.
Raw chicken wing...let him chew on that and not mom.

LOL ill try the chicken wing but all our baby food here has veg or pasta in it we dont seem to have just plain meat ones.

Look for either Beech-nut or Gerber.

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Where do you live?  N Bones are chewy and help with the chewing instinct.  We've only ever used the chicken flavor.
http://www.ferret.com/item/n-bone-ferret-chew-treats/650816/

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I'm in the UK,  we don't seem to have a lot if ferret things here.. Its more for rabbits etc. 

Ah.  Yeah, lots of ferrets but not so many ferret products.

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