Thanks for the responses - very helpful.
I have a request out on "Findapart" - had two negative responses so far, but I suppose something might turn up.
The bloke who sold me the seat now says he has found the bracket, so I'm in the process of negotiating with him (with my fingers crossed).
If that all falls apart, I may take up the offer of photos and dimensions - thanks for that offer - I'll pm you on that if it comes to that option.
I had intended to convert the cowl so that it can be used as storage, so I would be interested in how others have done it - thanks bloodbikes - I'll pm you about that.
Again, thanks for your help.