It's been over 50 years since small fiberglass yachts became available in the UK and the market for these small mini cruisers literally exploded. As yachts have got bigger and bigger over the intervening years, these small craft have been crowded out somewhat by the big boats and expensive marina charges. That said they can make a perfect small day sailor with the benefit of somewhere below to make a cup of tea or have a snooze while at anchor compared to an open day boat.
There are undoubtedly some tubs around from those days especially the experimental 60's and the unrestrained 70's but equally there are some good examples and while not suggesting these particular boats are in the bargain basement catagory, many can be had for a song.
Back in the day there was a bit of a fad for bilge keelers, some of which unhappily sailed sideways rather than go to windward so research and careful choice for the intended type of sailing is required.
There are also some tough little offshore cruisers among them, we met an Newbridge Virgo Voyager (like the second pic down) which had sailed to the Azores from England, A club member from the RAFYC had made several channel crossings in his 25 foot Westerly Tiger.