Gluten Free travel London

Hi All!

We have an opportunity to travel to London in the spring for one of my kid's sports.

Doing a bit of a hail Mary and trying to research options that will convince my gluten, dairy, corn and soy free husband to travel.

He absolutely will not eat out. Looking for what we can source locally that could be easily made in a hotel. Do hotels in London typically even have microwaves? Would a kettle be a possible option?

His meals typically consist of rice, beans, sweet potatoes, sometimes tuna with mixed greens, cooked ground turkey, chicken, and rice pasta.

Only places he will ever eat out are places that are dedicated gluten and dairy free (so some bakeries and a local French fry place)

Any ideas for international travel? I don't think I'll convince him but want to put some effort into trying. He's a bit of a fatalist with travel.

Most recent trip was doable, but it's pretty anxiety inducing for him. I think this will be better because it's not theme parks where we can't bring in outside food.