Jesus, I would rattle the hell out of her
But not at those prices 
I've gone for 15 minute P&D parlour punts before and quite enjoyed them, I know some punters book an hour and build up to a finale and for others they perhaps need that long to be able to orgasm.
I could actually consider a 5 minute P&D which is literally a wham bam thank you mam and her intention is possible to hook in punters who won't pay much more than that amount for a 30 minute session

Perhaps if it was £50 or if it was 10 minutes she would have more interest

Edit - Just looked at her profile and she's up to £80/5 minutes but that may be due to the location showing as Knightsbridge