He sold out 50 concerts for his upcoming comeback tour. 50 straight concerts in London. In a stadium that's easily 200k in size. That's over a million people willing to apay to see Michael Jackson. I'd say he was still a popular performer.
There are plenty of technical economic reasons to keep using the pound. There is actually economic freedom to be gotten from not using the euro. They might not be good reasons (although I think they are), but they are there. It's not just sentimentality.