just two thoughts
1) wetwipe type towel's that get thrown down the toilet. can cause blocks and a real PITA
2) when you replaced the bath next door did you replace the waste? does this waste connect into stack down stream of the toilet? it is a possibility (seen it done by a first year apprentice) that you may have pushed the waste pipe too far into the stack causing a blockage when the toilet is flushed.
1) wetwipe type towel's that get thrown down the toilet. can cause blocks and a real PITA
2) when you replaced the bath next door did you replace the waste? does this waste connect into stack down stream of the toilet? it is a possibility (seen it done by a first year apprentice) that you may have pushed the waste pipe too far into the stack causing a blockage when the toilet is flushed.