First of all, let me say that I rate the UK controllers as one of the very best in Europe, if not the best. It really is a pleasure to work with some of you guys in London for example, who maintain a calm gentlemanly voice (or the female equivalent) in the most busy airspace I know.
However, may I comment on one little issue? For a non-native English level 6 speaker one pronunciation is very difficult to understand, namely the way you say 2 and 3.
Why? Some UK controllers pronounce 2 as 'tueuei' and 3 as, well...'tueueuei' in stead of 'too' and 'tree' as per CAP413. At least, that's how it sounds to my non-native ear. So 'climb level FL230' sounds like: 'climb level tueuei tueueuei zeeeereu'. With as a result that two pilots are looking at each other asking 'was that 220 or 230?
Again, this is not a rant, it's just an issue which I deal with frequently in London airspace and which I thought I might bring to your attention
(and I know us pilots are much much much worse communicators)