I've used them sometimes in the past, albeit never as my main "broker", up until about 4 years ago. (I didn't stop using them because of any dissatisfaction with their service or concerns about the safety of funds with them, and I never had a problem withdrawing funds from my account, which I did on many occasions.)
They're certainly well regulated, and my overall impression was that they were about as honest and reliable as any spread betting company can be.
I'd be extremely surprised if you ran into a problem over either deposit safety or withdrawals: they're not a dodgy, Cyprus-based, barely regulated spot forex "broker", after all.
It's probably worth asking people whose experience of them is more up-to-date than mine, of course, but be aware (if you're not already) that very many online/forum/review negative comments about spreadbetting in general arise from a combination of ill-informed opinion, out-of-date "facts" and prejudice.