Good question, sometimes i do wonder why we bother, and i live not too far away from what many UK divers would consider "good UK dive sites" (St Abbs one hour away, sound of Mull 2.5 hours away.)
I quite enjoy the challenges that UK diving has to offer, and in the summer it can be quite pleasant, but in the winter it becomes more like an SAS survival course than "fun." I was diving at St Abbs yesterday, and it was bl@@dy freezing, very little in the way of life (not one fish to be seen,) and suiting up was an endurance session in itself with the air temp.
I have heard people "raving" about the great wrecks we have, and i would agree in part, but the problem is that the vis more often than not is poor, meaning you don't actually see very much at all (Scapa Flow for example Kromp Printz Willaim, massive ship and 3m vis.)
Given the choice, i would rather have diving on my door step where i do not sit in the car with my girlfriend (buddy,) prior to a dive, in February, when it is p!ssing with rain outside and freezing, trying to find a reason to get in the water.
My ideal would be, being able to get into the water in a wetsuit on, which does not require 12kg of weight, slipping into warm water with good vis and loads to see, and blue sea (i think i may be dreaming though.)
Having said all this, when the diving is good in the UK, and the visibility is good, i would not want to be anywhere else, it can be (on rare occassions,) some of the best diving in the world.
My final ten cents worth, because of the crud diving conditions we are subjected to, i would argue we possibly produce some of the most competant divers in the world, which can't be a bad thing.