The search engine on here sucks, so apologies if this has already been posted.
Not my favourite film, but animated Blu-rays are always nice. Surfs Up Blu-ray is available for just £5.98 from Amazon (looks like there's limited stock), or £5.99 from Play. Play's offering is probably a better bet considering possible Quidco/TopCashBack and higher levels of stock. Might be nice for the kids? Next cheapest is £8.85 from TheHut/Zavvi.