Got a night off from the kids, what to do?!

[Anothernamechangeee]

MIL kindly taking our 2 DDs for a night, they’re 3&1 and this is our first night away without them. I can’t bloody wait.

where to go and what to do? We are south west London so anywhere an hour or so away.

Easy. Go for dinner at somewhere nice, maybe even your first date restaurant, if that applies. Enjoy yourselves, and spend money (not lavishly), but enough to feel nice. Your goal should be to rekindle that "oh my god I'm a teenager falling in love" feeling again we all had.
Afterwards, since you have a free house, continue the hopeless teenager theme and go at it as best you can, for as long as you can, as many times as you can. With a pinch of salt - you probably do not want that third child. With a pinch of spice - make it different. You know each other very well I'm sure, if you have had kids together. Therefore, there is no reason to be ashamed of any kinks you may be interested in exploring. (Or toys, roleplay...you get the idea.)
You will feel much better for it.
How often do you get this chance? Take it while you still have the energy (probably libido, realistically).
Hope this helps, and have fun.