Correct on all counts! Back to you, sir.
The constituent parts of the 18/6 outlay were:
5/- fuselage
5/- wing
8/6 fittings, dope, etc..
Those were the days when you could make yourself an aeroplane for less than a quid!
And in response to your question, the answer is no. The information came from 'The Story of Gliding' by Ann Welch - which has been in my library for more decades than I care to recollect - and my own research, which appears on another forum, concerning the Itford competition (q.v.
http://sussexhistoryforum.co.uk/index.php?topic=2277.15). If it interests anyone, there is a good deal on that forum concerning early gliding in Sussex and the county's pre-war gliding clubs.