Sunnybob,
Glad to be of help.
In fact there is very little information in the book other than what I have posted but the details are:
Scale Model Ships - their engines and construction by Bernard Reeve and P.W Thomas.
Published by Sidgwick and Jackson Ltd, London. First published 1951, reprinted 1959.
I'm afraid I can't part with my copy as it was a school class prize in 1962/1963!
As far as the Shipwright plans are concerned, these consisted of two sheets, General Arrangement and Deck Plan Ref: MC 23/1 and Hull Lines Ref: MC 23/2. The plans were at one time ( in 1985) available as part of the Harold Underhill collection but they are not mentioned in the current listing from Brown, Son & Ferguson who currently market them:
http://www.skipper.co.uk/catsmp.htm It might be worth making enquiries of BSF as they may know what's happened to them and can put you in touch. It's rare that model plans go missing entirely but it can be hard to track them down.
I think that just about exhausts my knowledge but I'm pleased it's filled a gap in your family history - these things are important.
I found the pictures by Googling "Osborne Littlehampton". It's possible you might be able to get more information by contacting the people advertising the full size vessels for sale. They were obviously quite famous in their day and there may well be more documentation available from enthusiastic owners. If you do get any more info give us an update on here. It's a lovely looking "little ship" and makes an impressive model.
Cheers,
Colin
p.s. I've changed the title of the first post to Gwen Eagle which will alter the topic title.