Not strictly cosha and genuine, but you can remove the HT leads and replace with normal HT leads, albeit with the ends cropped so the lead fits into orifice in dizzy cap and then you can run normal LR plugs to suit 2 1/4 engine. After all ignition side of engine is 12V when running!
I owned a S3 FFR 109 and had problems with screened plugs that became expensive. Fitted the above and didn't have the same issues.
I managed to buy brand new points from The Landrover Orphanage, as they has quite a good spares list for 24v Series LR's. LR Series is my other favorite shop. Craddocks and Blanchards also cover the 24v FFR's.