What I did, and what I'd suggest is to look at each bolt in question. Some, ie seat belt bolts and structural bolts, need to be as high a grade as you can get, zinc plated grade 8 should be fine. Non structural bolts, ie those holding the fender sides to the inner fenders, trim bolts etc that bolt aluminum to aluminum should *not* be stainless. This is because stainless is about as far away on the galvanic scale from aluminum as you can get. The resultant corrosion would sacrifice the aluminum...something you don't want to do. Aluminum bolts aren't known for their strength, that's why I only use them in situations where there's high corrosion potential and little strength needed.
I'll use stainless where I don't have a worry about galvanic corrosion. Also, keep in mind that the strongest stainless bolts, will only be grade 5 or so.
Something else I'd recommend, is insulating between dissimilar metals upon re-assembly...I use self adhesive neoprene strips for this...
I'm in the US and I get my supplies from McMaster-Carr...not sure of a source in the UK...
Stainless is an alloy of steel and nickel which as bogatyr says will destroy your ally panels in no time use good quality BZP (bright zinc plated) nuts and bolts that is why I asked what you wanted them for you were however correct in doubting the quality and cost of items from the likes of B&Q etc.I use M6 BZP items to relace the 1/4 unf bolts and M8 BZP''s to replace 3/8 unf bolts.these are cheaper and more readily available I get all my supplies from a company in Barrow-in-Furness called INFAST they are suppliers to the Shipbuilders in the town so are of top quality.
Look for Dacromet coated fixings.
Dacromet is a non electrolytic coating with the same or better corrosion resistance as zinc. It is often black but can also be coloured.
Try a Google search for a supplier.
Sorry, can't help . I would just spend the evening searching the web.
Dacromet coating is specified by Rover for various fasteners and their part numbers fully describe the screw, bolt etc. Trouble is, I can't remember the codes :dunno: and buying single bolts from a Rover dealer would be too expensive anyway .
You could perhaps contact a metal coating company and have some standard fixings coated, or just stick with zinc and use plenty of grease .
LR Fastners (advertised in the magazines) produce kits for various parts of the vehicle. I have recently recieved their full 109 body fastner kit, plus a few specified extras. The kit is huge, and has every nut, bolt, rivet, washer and bracket for al sorts of variants, including spares to allow for the inevitable dropped nut or lock washer. He packs the whole kit into small sealed palstic bags for each individual job (eg. 1 for brake pedal box, another for clutch pedal box), with the sealed bags being grouped into vehicle regions within the pack (eg. bulkead, rear tub mounting, roof mounting, doors, etc.)
He's not cheap, but it all sems top quality, and I hate to imagine how much time he spends (and thus saves customers) counting, separating, packaging and labeling each measure of fastners. Worth every penny.
When assembling, use a smear of copper-ease onthe bolts, and once finished, give them all a quick spray with some waxoil. That way, you'll have the correct spec fastner (size and strength), protected for eternity by a coating that inhibits galvanic corrosion, rather than accelerating it.