We've found UK self-catering holidays to be ok with a young DC. But we do ensure there's someone else there for at least part of the holiday too 
Either my parents share the holiday with us - not ideal in some ways, but does mean DP and I can get some time alone - or we invite friends, with or without DC, to join us for a few days.
Going in the car you can take half the house's worth of toys with you, and the gro-clock and all that malarkey to try and make things seem familiar for very young DC. Always have separate rooms too, sharing a room with DC sounds awful to us.
Then also we admit defeat and plan things around what a 3yo will find interesting - a walk in the woods, a horse sanctuary, rockpooling, that sort of thing. As a PP says, just take things slow and enjoy the break and the scenery, rather than trying to cram lots in.
Self-catering isn't everyone's idea of fun as you still have to wash up and cook meals and that, but we do end up with quite a lot of takeaway and buy picnic style lunches to cut down on the cooking. So there is still quite a bit of "same shit, different location" , that is true.
Personal taste though. I couldn't imagine flights and hot sunshine and hotel rooms with a 3yo (I can see it when they are older and you can pack them off to the kids club all day!), but I know lots of people much prefer than and would hate to be in overcast Norfolk cooking their own food for a week.