On my property, to the rear of my house, I have a foul drain chamber that is frequently getting blocked by thick toilet paper and whipes etc. Is there any safe chemical or commercial product I can buy that will help break up or dissolve this blockage and restore a good flow.
Not that I know of and even if there was, it wouldn't clear a blockage such as this.
I would suggest you investigate who is flushing wipes and thick toilet paper (kitchen roll?) down a toilet. The only product of this nature that can be safely flushed is toilet roll as it is specifically deigned to break up in water and therefore should not clog the pipe. Everything else should be binned and not flushed.