UK isn't that hot compared to California, and I would suggest that virtually anywhere inside, and out of direct sunlight would be fine. So an interior room, or shower would be very good. There will inevitably be spills and drips so keep that in mind. There are many yeasts that work well and will tolerate warmer fermets. Avante yeast for instance, lists an upper temp limit of 95F (35C). Highly doubtful you'll go much above 80F (27C). I ferment in my garage which can be cool at night but quite warm in the day. I use a floating thermometer to keep track of the temps. The highest temps in the must I have ever seen is around 85F and my climate is much hotter than the UK.
I would not use Montrachet yeast your first time out. Too many reports of H2S unless handled perfectly. If you are making a kit, I strongly recommend you just use the yeast in the kit. It will be "engineered" to work well most conditions with that particulat kit.
With your first fermentation you'll want everything perfect, but after awhile, you realize the process is pretty forgiving. And, your first vintage is not about making a great wine. It's about learning the process so you can make great wine later.
What volume are you doing? That plays a role, because larger volumes generate more heat and the container will typically have less surface area to dissipate that heat. If you are just doing a typical small batch like 20L, don't worry about it. If you feel it's too hot, set your fermenter in a tub of cool water.
Good luck.