I normally use the Clean & Safe disinfectant stuff from Pets at Home once a week. If they are really mucky you can use vinegar and it dissolves all the stains off. I did that last weekend, boiled it up and poured it in. Did my old litter trays too which were really stained and they came up looking like new!
Wilkos rabbit hutch cleaner is really good on the inside of the hutch but takes some scrubbing on the litter tray... I might try the vinegar trick! :thumb:
I use the clean and safe stuff and give them a quick wipe with kitchen roll. I do vinegar them occasionally but as I use it to discourage them from peeing places I try not to too often and give them a good rinse after, in case they decide not to pee in them after!