It feels as though you may not be telling the whole story here:
Hi all, a leak from my flat caused a leak to the flat below a while ago
and with the pandemic I had explained to the tenant below that I will repair this when things are okay (ish)
and she was fine with that (she obviously wasn't and told the agents).
I have had the block agents chasing me to get this fixed this past week
Exactly how long ago did the tenant below first report to you that water was leaking into her flat and causing damage?
Were you planning to repair the damage yourself or arrange for someone to do it? Which did you tell her?
Did you give her
any indication of time it would take you to do this?
If you were planning on arranging someone to do the work, then why didn't you do this?
What
exactly did you write to the block agents in response to them chasing you to get this fixed?
If it seemed to them that you were just fobbing them off with more delays, then it seems entirely reasonable that they arranged for the work to be done at your expense.
While I accept liability and I am more than happy to pay for the works but the £500 seems very excessive for such minimal work.
If it really is such minimal work, then why didn't you get it done? The tenant in the flat below has been living with the damage all this time.
I am clinically vulnerable so this past year has been difficult for me
I'm sorry to hear that - but surely you still could have picked up the phone to arrange someone to fix the damage?