Many thanks for the extra information Dermot,it may help others who have DS4s.
My present '31 Box has a DJ4 for which I had no problem obtaining parts for.

Location: Near M1 Jcn 28

Brian,
The rotor arm was new when I bought it many years ago but it was a very loose fit on the shaft even then so it always had the tape on it to take up the play.
Cheers,
Dave

Location: Sheffield

Just in from the shed and have two N.O.S. boxed (Remax)rotor arms for DS4 distributors.

Ruairidh, I have left a message on your email address as shown on your posts.
Dave, thanks for the info, I have probably been worrying needlessly and will try your tip.
Rob, your reply is excellent and provides numbers to look for at autojumbles.

Location: Near Jtn 28 On M1

Nicely found Dermot!

£16.42 here: https://www.smallfordspares.co.uk/products/ye-12116-a-distributor-cap-32-35





£7.72 here: http://www.ebay.co.uk/itm/Rotor-Arm-for-Vauxhall-Viva-HA-Series-Van-Delco-1975-82-/390349760840?_trksid=p2385738.m2548.l4275