Uk Platinum is not difficult to get at all (Well I didn't think so), I held a Gold card for just over 4 weeks, charged just over £1000 to it and was upgraded to Platinum, I just told them that I didn't have any problems with the £225 annual fee. The minimum income requirement for Uk Plat is same as Uk Gold £20k, but obviously they do prefer if you have a higher income and monthly spend.

Centurion is a completely different matter, They can be as picky as htey want. If you call them up you'll get every answer from £1500 per month to £10000 per month. I would say £50-75k in one year plus held Platinum for at least 1-2 years should help you along the way.

Thanks,
Rich