I would say the 145l rub bin would be good too - a good size for a pair. It's the biggest bin I know of but not too big. They're not that cheap but they're supposed to be easier to cut without cracking.
Go Shopping - Really Useful Boxes - 145 litre Really Useful Box
Internally it's about 71cm by 45cm. Seems to be slightly cheaper on Amazon.
https://www.amazon.co.uk/Really-Usef...lly+useful+box