The Working Time Regulations 1998, PART II, Regulation 10 says
Daily rest
10.—(1) An adult worker is entitled to a rest period of not less than eleven consecutive hours in each 24-hour period during which he works for his employer.
Entitled is the key word here. I know that I can opt out of the 48hrs per week limited as per this page
You can opt out for a certain period or indefinitely. It must be voluntary and in writing.
but I can't find anything whether it's fine to do it on daily rest.
Yes
If you look at the law pertaining to the work week and opting out of the maximum, which is also in The Working Time Regulations 1998 (with my emphasis in bold):
4.—(1) Subject to regulation 5, a worker’s working time, including overtime, in any reference period which is applicable in his case shall not exceed an average of 48 hours for each seven days. ... (3) Subject to paragraphs (4) and (5) and any agreement under regulation 23(b), the reference periods which apply in the case of a worker are ...
So if we go to 23(b):
- A collective agreement or a workforce agreement may—
(a)modify or exclude the application of regulations 6(1) to (3) and (7), 10(1), 11(1) and (2) and 12(1), and
(b)for objective or technical reasons or reasons concerning the organization of work, modify the application of regulation 4(3) and (4) by the substitution, for each reference to 17 weeks, of a different period, being a period not exceeding 52 weeks, in relation to particular workers or groups of workers.
