Hi Andrew, I've done a little bit of digging in the Cherub history files on "Scrummy" 749. Assuming the sail number of 749 is correct, and I suppose we can be pretty sure it is, given that it's engraved in the hull, that puts your boat as being built somewhere about 1963 or '64. That means it's over 50 years old! This is a serious classic of the fleet. Unfortunately old boats rarely have much financial value, but in terms of historical interest and importance it's way up there. The only older sailing Cherub I know of in the UK is Wanderous 698, owned by the Lee's (although may have changed hands recently).
The sail number list went up to 750 and then jumped to 901 due to different countries being given different batches of numbers. The 1965 Nationals were won by Cherub sail no. 920, 2nd place Hart-ta-Beat 738, 3rd place Micro 907. So your boat certainly pre-dates 1965. Gregory design boats were popular at that time, so it's quite possible yours is also one, probably a Greg3 or Greg4.
Also of note is that 749 was originally registered with the name "Julia". Maybe the owner fell out with his girlfriend or something and re-named it "Scrummy" after the other woman. That's my theory anyway.