OK. 2 points - i) for band 6 that is actually very good but ii) With 4.5 years experience, I'd be pushing for band 7. It's possible that the salary wouldn't be much different (the bands overlap a lot) but for obvious reasons it will take you a lot less time to get to band 8 if you start at band 7. Band 6 to 8 could take you over 5 years even if you're very good, dependent of course on many factors.