In the last 12 months I have had 3 months for 99p, 3 months for £3.99, and my latest is 3 months for £1.99. I cancel then within a few weeks they come back with a new promo. My current membership will be cancelled in two weeks, just before my next payment (full price) is due.
The normal price for a 1 month 1 credit membership is £7.99. I feel i've done quite well