Which is the best to use in wheel wells etc, and where is can find a good supplier?

Cheers fellas!

Any of the big DIY places should do both, especially if they stock electrical goods. Solder can be a mite expensive, especially if you buy the new(ish) lead-free. It's normally possible to buy a card, of fuse-wire, with lengths of 5,10,15 amp wire, for only a few pence (different amperages are different thickness.) It's rare to be able to buy short lengths of solder, in varying diameters; usually it's thin, or thick.
Edgar

Another source would be a fly tying shop. Here in the States we can buy spools of lead wire in varying diameters. Fly tyers will wrap the wire around the shank iof the hook to add weight, then finish dressing the fly with fur, feathers or other man-made product.

I have several sizes that I use for my 1/48th scale aircraft: .01", .015", .020" and the jumbo .03".

Good luck.

Check old electronic devices too.
I know computer devices that have wires have smaller internal wires that are great for these uses. Mice, Keyboards, old network cabels etc.

Jan

Vaious sizes of wire are available in your local Jewellery making/craft shop - or in my case in SWMBO's craft case :-) :-) :-) :-) :-) :-) :-)

Andy