For those who prefer additional comforts, I’m sure the Sofitel Is a great choice. However, as the OP has already told us a usual haunt, which suits perfectly, is a Premier Inn then I fear expectations of price v convenience are not going to be met by a 5* property, even with some of the discounted mystery hotel rates,
OP, if you have a car then many of the Bath Road hotels will suit you just as much, particularly if they offer a parking deal given it’s an easy free bus ride to T5. There’s a much more varied range there than at T5 (and definitely don’t be fooled by some of hotel descriptions - it’s quicker to get from Bath Road to T5 than from some who you might think are on top of the terminal!).
You may be better suited heading over to the UK & Ireland forum (
https://www.flyertalk.com/forum/u-k-ireland-484/) where this regularly comes up for discussion.