When do I tell uc about my rent increase?

My landlord wants to put my rent up and he's tried to do so by means of a new 12 month tenancy agreement. I've told him I won't be signing a new agreement as from the 1st of May it won't be worth the paperwork it's written on so there's no point to having one for 2 weeks (and because I know he can still increase it again via a section 13 if I agreed to it this way). So I've requested it via a section 13 (knowing that that means he can't increase it again for a year). I currently get the max uc housing element I'm entitled to for my 2 bed flat which is £875, and my rent is currently £1000. Meaning I have a £125 top up. But he's increasing it to £1085, so I'll then have a £210 top up. Now I know I won't get any extra help from uc but I still have to tell them, right?

So these are my questions…

When do I tell them? Do I tell them on the excate day that my section 13 says the rent is increased by? So if it says on section 13 from 23rd May the new rent is £1085, do I tell them on 23rd May? Or do I tell them before? If so when, like when I receive the section 13?

How do I tell them? Do I tell them on my journal? And do I upload pictures of the section 13?

And will this trigger a change of circumstances and possibly effect my transitional protection (although I believe it won't as I already asked this previously), or possibly cause them to relook at my whole claim again?

Thank you in advance for your time and help, I really do appreciate it.