I just got an email from See Tickets with a special offer where the top tickets normally costing £63.25 are now £25 until midday tomorrow.
The site adds on a £2.75 booking fee for collecting your tickets annoyingly.
No cashback on TCB or quidco.
Valid on Monday - Friday performances, from 5th September to 15th October.
Book by Friday 2nd September 12pm.
Hope this helps somebody!