I've got a Q500 it's very good but I wouldn't call it small, it's got a 4K camera and all the clever functions, if you want something small with a decent camera then I would go for the spark with the remote, you are then looking at £650+ with two batterys
if you do go for a Q500 get the pro pack as you also get a handheld gimbal and two batterys,it's got the st10 tx with its own screen and you will pick up a decent used one for sub £500