Bad smell of sh1t

We got connected to the mains 7 years ago. In the last year or so there has been increasing issues in relation to sewage smell.
Basically if water dries out somewhere, the stench is like very strong sewage. For example, if the trap in the shower is left up after cleaning it and dries out or the whb isnt used for a few days and the u bend dries out , or the toilet gets a bit blocked and there is no water in the bowl...in the first and last scenario particularly, you get a horrendous sewage smell inside of an hour or two.
I'm worried that there is an issue and somewhere is a big blockage causing this back draft of stink.

I've never had this before in other houses or before we moved off the septic tank.

Furthermore, and it may or may not be a separate issue: the toilets block quite easily ( I have young children that regularly use too much toilet roll and block the toilets).
One of them leaks from the back of it (enclosed cistern) if it gets clogged - I e. Out the waste pipe. Water spills out from the cistern cover box where the waste pipe is also contained.Once it's unblocked it seems to reseal itself for the most part. Occasionally it also emits a rancid sewage smell.