BT have tweaked their deals again, so I thought this looked pretty good if you are already a BT customer. I was on the 4GB / 500 mins plan, but switched to this.
Essential plan - 6GB data / unlimited mins / texts £11 PM, but this deal can be made into a family plan, so I've now got 5 of us (Me / partner + 3 kids) all on the same deal for £37 PM total or £7.40 per SIM per month which I thought was pretty good.
Also a £30 amazon card plus some quidco (maybe 25 or 35 wasn't sure)
Lastly BT are adding Roam like Home from 15th June so you will be able to use you minutes / data / txts allowance in 47 countries http://www.productsandservices.bt.com/mobile/data-roaming/