The 2240 has to offer the best bang for your bucks. An excellent accurate full power pistol but I would replace the plastic breach if it is going to get handled by a lot of people (you would also have to fit replacement sights). The pistol, breach and a cheap red dot could probably be had for £150.

The EB22 is a similar pistol and you could also consider the crosman 357\vigilante if you wanted a cheap, accurate multishot. They are plastic but have a good reputation.