Backdated rent increase to 1st period and Transitional Protection

I was migrated to UC from legacey benefits two assessment cycles ago, and have been award Transitional Protection.

The issue is I didn't realise rent increases would erode this. My rent has gone up in years, and it's £715 compared with the £900 that the now 1 Bed LHA locally is now set. If I moved I could increase the LHA to £900, but the TP would erode by £185, and i'd be 'out of pocket' that much.

I didn't realise the Housing Element was in the TP, stupidly, and I discussed the increase with my landlord. We agreed a verbal contract we will both honour, and can provide testimony, for within the 1st assessment period. I just thought it could be backdated or go up later when I setteld the payments and understood them better (my case is a bit complicated with premiums).

If my rent were now to be back dated to £900 in the 1st period, would I lose the TP? The variance in cash terms doesn't matter to me as much as getting the £900 level going forward. It just needs to apply since then and ill absorb the cost to cover the arrers out savings. Obviously I dont want to lose the TP for merely this, as it's value higher.

Probably a bit complicated, so if there is any insight without certainity that is still welcome. Along with any suggestions as to where to get some authoritive advice. I know a solicitor who can help...

OK, there are serious health complications in this period which I believe are legitimate grounds at least to ask.

To be clear if the rent increase is that only applied after the 1st AP, then the LHA would go up and the TP would go down accordingly to 'balance'?

I'm just trying understand whether that is going to mean this would be a 'new claim' and completely void the TP awarded presently. It's also so complicated and the lack of clarity make me ill.