DRAIN BLOCKED..TOILET NOT FLUSHING..

After you get this sorted out, if you or your household use wet wipes/make up remover wipes of any description, don’t!! They are a well know drain blockers because they catch on the rough pipes and build up.
I hope you get help soon.

I don't know if it's the same where you are, but when we called Thames Water out to deal with a blocked drain they didn't charge us as our drain is shared with the adjoining house.

I agree you have a blocked drain. If you were able to lift the manhole cover the level of water etc would be very high. you'd need a set of drain rods at the very least, either that or call someone such as dyno rod etc to unblock the sewer for you. I know nothing about HA but I'd tell them it's urgent and requires immediate attention and if the don't send someone immediately I'd call a drainage plumber out and send them the bill because you can't be expected to live like this.

Definitely call your HA as an emergency. I worked for HA's for 30 years, contractor should call ASAP this evening.

It sounds like a drain blockage. The HA should have an emergency service on call for drains, other than that the main water/ sewage provider ( Severn Trent, Anglian Water, and the like ) will deal with it if the blockage is in the main sewage drain.
It phone the HA on call service straight away.

I do feel your pain. We bought a property abroad and we’re told we had a septic tank. Given all the info as to the emptying etc. We never did have a tank. ?

This isn’t a blocked toilet. This is your drain. Can you lift your manhole cover? Maybe don’t ? it won’t be pleasant.

pour 1/2 a bottle of washing up liquid into the toilet, leave a few minutes, it lowers friction. Then have water ready and flush and pour water at the same time. Repeat, the blockage will go down

You need a plumber out ASAP, hassle your HA nonstop, and if necessary and you can manage it, get the work done and send them the bill for a refund, cc'd to your MP