hmm, you could be lucky and the petrol has just agitated some crud in the tank, blocked your filter again. i'd try replacing it again just in case.
it is possible that the seals in the fuel pump have warped/perished with petrol. there is a fantastic guy in the north, diesel bob. he can diagnose, repair, etc. diesel pump/injectors/etc. and is very reasonably priced. i found the diesel specialists local to me (midlands) to be really expensive for high pressure (common rail) diagnostics and repairs.
for the record, a small amount of petrol (say 10%) in your tank will not do any damage, in soem cold countries they add it as standard to stop the fuel gelling. but pure petrol will cause damage.