can anyone recommend me a shed/ timber building supplier for bike storage/workshop/'man-cave' activities?

get a local firm to supply you a shed to your exact specs it does not cost much {if any} more than one off the peg

ideas for specification and design would be welcome – needs to store 4/5 bikes what other essential features should i be planning?

One of these, in the 10×8 flavour.

I'll be buying one this month for the new house, should store 4 bikes, loads of gear and aneough room to work too….

http://www.tigersheds.com/product_detail.asp?prod=15

They want £800 for the same shed locally…..

Security shed it has to be, more battens, and tiny windows… anything to deters scrotes.

love that one "man cave"

I'd recommend getting bigger than 10'x8' if you have room in the garden, unfortunately I don't. Once you get a work bench, bikes and garden furniture etc in there the space soon goes!