Thanks for the replies everyone. In a way I'm glad its not just me that has or had the problem
The all metal ones seem to fit fine, it's just the two 'two wire' holders that are the problem. The bulbs do screw in OK but haven't electrically tested them fitted yet.
I'll go with the Superglue method first as dont really want to cut a brand new harness about. If that doesn't work then more drastic measures may be the only answer. I think I have some originals on another loom. HOY's original loom was butchered beyond belief and the holders were missing !!!
Norman, apart from this issue the loom is very good, the earlier issue I had with front fitting was my misunderstanding of how it actually ran along the slam panel.
These holders are definitely something that should be addressed.