Flat cleaning

You are best contacting a few companies directly for pricing.

You could ask for a deep clean to start with (which will be much more expensive), then a normal clean going forwards which should be less money.

It might be an idea to get one company to do the deep clean, then another company or individual to clean regularly afterwards.

This is what I did for my Mum, as "normal" cleaners wouldn't touch her place the state it was in before the deep clean.