Hi Brucie,
Three years ago I had bottom end of my engine done by T&L Engineering in Elstow, Beds (
http://www.vintage-engine.net) and have had no problems. Cost was just short of £800 including VAT. I didn't have the end feed conversion done as the mileage I'm likely to do on her doesn't, in my view, justify the cost.
Below is what they did - dynamic balancing of the crank was £150 but well worth it.
DEGREASE/HOT WASH COMPONENTS
WELD CRACKED SUMP THREAD AND REPAIR THREAD 1/4"BSW
FIT CRANK CASE BREATH PIPE IN DRIVE SIDE
CLEAN OUT SLUDGE TRAP AND FIT NEW PLUG
REPLACE TIMING SIDE MAIN BUSH, FIT NEW AND BORE TO SUIT CRANK
BALANCE 2CYL. PARALLEL TWIN CRANK . PISTONS AND RODS (ROAD)
REGRIND B/E MAINS M/C TWIN INCL. NEW B/E BEARINGS
MAKE NEW BUSH TO REPLACE SPINNING BUSH ON TIMING SIDE
STRIP AND REBUILD BOTTOM END OF ENGINE
DRIVE SIDE MAIN BEARING
FIT AND SUPPLY DRIVE SIDE OIL SEAL
FIT HELICOILS IN T/SIDE CASE
MISC BREATH PIPE DRIVE SIDE