(09 Feb 2015, 7:06 pm)Adam wrote haha. I've looked at the prices and they are capped. We've ordered ones covering Zones 1 & 2. For the buses, it's £1.50 for any single journey, with a cap of £4.40, so you could ride 20 bus journeys and it would still just cost £4.40. As for the Tube, it's a £2.something single for Zones 1 & 2, with a cap of £6.something, so the maximum I'm going to spend on transport whilst down there is £11 odd

You won't spend more than £6.40 in Zone 1&2 on pay as you go as it's capped at that price, no matter how many journeys you make.
If you get chance then I'd definitely include a ride on the DLR, and I would have recommended the Emirates Air-line too but this is in zone 3 (North Greenwich-Royal Victoria). A trip on the Thames Clipper boats down the River Thames was great when we did it in 2012 (at the end of a very long, but superb, day out) - it was just getting dark and everywhere was lit up along the river, we did Woolwich to Embankment