Checked Home Bargains after work today. No Planet 51 toys, you heartbreakers.
Maybe it's just the shops down South?
EDIT:
Just checked today and although still no sign of Planet 51 toys, they do have Optimus Prime bubble bath for £1.99.
It's
big. I didn't buy one so I don't have the exact measurements but it's at least a foot tall. Would make a great starting point for a battlemech conversion.