Hello Howard, within the set of drawings you bought for £19.50 should have included the copy of original AEROKIT plan and side elevation, plus a poor copy of the instructions in reddish print, these are the only reliable and accurate details, the rest are very poorly drawn out and frankly inaccurate even down to items 1,2 (two part keel ) both are wrong despite the AEROKIT copy plan being correct, as for your renovation I have renovated many models and also built many models including two Griffon 2400TD RM hovercrafts and two MGB 81 (last gunboat still at Portsmouth) so if you need any hep with restoration of your RNLI just drop me a line.
Best Regards
Barry