I stumbled on this today....
http://www.ebay.co.uk/itm/EWS-Delete...#ht_500wt_1361
It might be of interest to Timbo or anyone else considering a M52 installation.
I think Tim's ECU was a later MS42 but I can't think why the engine would not run with an MS41? (but I may be wrong and I can't currently remember this difference)