If you are on a Uk passport you don't need a transit visa, not sure what that is about.
I have had a journey break like this many times, just collect your bags, go off to a hotel and then re check in the next day. When you check-in tell them that you will be collecting your bags. The only thing you have to check is if your ticket does not include the 700 baht departure tax you will need to pay that prior to check in.
I have stayed at the Dusit Srinakarin several times and there is plenty to do around there, but you could equally take the ARL into the city and grab a hotel there.