I am only really interested enough to punt once a week at most, even if I had unlimited resources, and at that rate I would probably still get bored before the year was up.
So, I would go for the 50 x £400 option. Lots of "specialities", duos, outcalls (£100 on a hotel still leaves £300 for an escort), roleplays where I buy them a costume. Got to get imaginative for that amount of money and not just blow it on some over-priced "pornstar".