It seems to me that you really don't have any major problems. If you are registered as a non-resident landlord
, your agent will be reporting the rents to HMRC. I'm assuming that no tax is deducted from the rent by the agent as it is so low and well below the personal allowance which is currently £10,600.
You are entitled to the personal allowance (at least for the time being) if you fit the criteria here
. HMRC may periodically ask you to complete a UK tax return so you should ensure that they have an address that you can be contacted at (the agent for example) so you will be aware if they do try to contact you.
If the personal allowance was withdrawn for non-residents in the future which is a possibility, then you would almost certainly have tax to pay in the UK on your annual rental profit if there was one.
If you want some peace of mind as to your situation as far as HMRC are concerned, then you will have to contact HMRC by calling the number here
. Ask them if there are any outstanding issues such as tax returns which need to be addressed. If you don';t have your UTR tax reference, your NI number should allow HMRC to trace your file. Your letting agent should have a non-resident landlord reference for you.
You might ask your letting agent if HMRC have contacted them to locate your whereabouts but confidentiality issues may prevent them from doing that. Certainly, if you had an accountant or tax adviser in the UK, HMRC would contact them if there were things that needed to be done.
As I said at the start, I don't see any major issues given that your rental income is low but it would be worth calling HMRC to find out for sure.
I hope this helps but let me know if you have any further questions.