I am sure that this is very difficult for you.
If you, as you say, are coming to England this month, be aware that all of England is under a lockdown until into December and possible (probable) extension. Restaurants and bars and most shops and most attractions are closed. Tourism isn't allowed. Unnecessary travel is not permitted. That's for everybody, after the quarantine.
I'm just seeing on our local news that if lockdown is lifted we will likely return to the tiered system. Before the lockdown, the area in and around Manchester and the northwest and northeast and northern Midlands was in the highest tier and will almost certainly return to that or even more restricted.
I am sure that supporting your partner's family is very important, but at the moment England is no place to come to.
We don't know what Wales will do in the weeks after the fire-break...