Hotpoint BF41 leaking from door during wash

Hi, we have a Hotpoint BF41 dishwasher which started leaking water from the door 1/4 way through its wash cycle. Not having experienced this before I replaced the door seal, to no effect! Opening the door during a wash the water level in the bottom appears too high (for the door seal to cope with). I pulled the unit out to check the level switch. This tested okay electrically and appeared to operate when gently pressurised by blowing. The tube connecting the pressure switch to the Put the side back on the machine and just did some cursory checks inside on the filters. There was some blockage on the secondary/outer main drain filter and so I washed this out and replaced. I thought this might have caused a scavenging problem to the recirculation pump. So we gave it a try and still the same problem! So, does anybody know the BF41 well and have experience of what normally goes wrong when water starts leaking a while after the start of the wash cycle? Thanks guys.