Since this question seemed to be oriented as to whether or not it's generally considered begging in the UK in specific...well, as far as I've seen it is actually more accepted in the UK and Ireland than here in the US. I have seen many buskers in both London and around the entire countries of Ireland and Northern Ireland as well as have busked myself in Galway. I do have to say though, that there is definately a quality line. Most buskers there are of a pretty high quality because the competition is pretty heated. So...nope it's not begging, but there is an expectance of quality..that's my general assesment.