Managing cash receipts when transitioning from UK sole trader to Micro entrepreneur

I’m about to leave the UK (~20 Apr this year) and set up as a micro entrepreneur, probably using the registration service here. As is the case with being a micro entrepreneur, my current regime in the UK as a sole trader uses simplified (“cash-based”) accounting, which means I only record cash received and have no P&L, etc.

The problem I have is what to do with cash receipts that come from invoices for work done earlier in the year. For example, I may deliver work in March which won’t be paid until May or later.

1) Should I account for these under my new micro entrepreneur status as they relate to “work” and are being received at a time when I’m already set up as a micro entrepreneur? My gut says no, but I’m not sure.

2) Conversely (and this is probably more about UK tax, so you may not be in a position to help) if I don’t declare these as receipts in my micro entrepreneur account, I seem to have a problem on the UK side — i.e. I end up recording amounts to be “taxed in the UK” but after I’ve become tax resident in France.

My understanding is that tax residence takes effect as soon as my main residence is in France i.e. ~20 Apr. I guess a third possibility is that these receipts from my UK business would be declared in France but not under my accounting as a microentrepreneur.

Grateful for any light you can shed on this.