Not been in that situ.
Looking on Parkers a dealer PX on an 09 Mini Cooper S, don't know your spec, so put 3 door with Chilli pack.
An 09 plate is £7935.00, a 58 plate is £7705.00.
They will probably put it up £10k on the forecourt, so they are probably being a bit generous. But it is a bitter sweet pill to swallow, always is after 12 months.