If you want to spalsh out on a more powerful battery than what the Poundshop offer. i.e. do you want your kids new toys to last till Boxing Day before you need to replace the batteries, then this looks a pretty good deal.
They have loads of different batteries eg 9V;AA;AAA in various pack sizes; all buy one get one free.
If they don't have any instore then you can have them delivered to your local Wilkinsons for collection for free.
Prices between £3.19 and £5.89