I've just had the same done to my bulkhead and am about to have it galvanised!

Any suggestions as to what is the best thing to paint the underside of my series three with?

Excellent, thanks for the really quick response! I take it I should be able to work out which bolt length goes where unless I'm dim (may be the case!). Also do I just apply a good coating of grease to the bolts, plates etc.?

About to start building my 1971 Series 3. Got all my new shackle plates and bolts but have no idea which one goes where! Some are threaded, some are not, some have a wider "offset" than others, some have no offset. Ordered all the new bolts also, some linger than others, no idea from the...