@Chris14085 I can't say what the regs are in the UK, but I'm sure some UK hosts will chime in.
As far as Covid safety, it sounds quite vigilant, which is good, and because both if you are vaxxed, and are into masking, and distancing, there's not that much risk, IMO.
If weather permits, I would try to keep windows open as much as possible to keep fresh air flowing, especially in the kitchen that you'll both be using.
I'm also a home share host with much the same set-up. Guests have their room and ensuite bath, and even an outside private entrance. They share my kitchen. I haven't hosted since last March, but once I get vaxxed, I will feel okay about hosting guests in much the same way you describe.
I don't know if you read the study that just came out of MIT, but something really interesting and important to know is that they found that in shared indoor spaces, 6 ft of distance doesn't really help. They found active virus particles floating in the air 60 ft from where they were released. So all this business where restaurants have indoor tables spaced out, while people are eating without masks, or gyms and yoga classes where people are spaced out, isn't even slightly safe. It's even worse if there are fans which spread the virus particles around.