Hi , had the same problem with mine, it's a different model but no doubt it'll be along similar lines, the filter on mine is under a removable plate at the front bottom, i removed it and most of the water drained , in the end i had to take the back off and remove the pipes from the drum to the filter which is just a couple of squeeze clips and maybe a jubilee clip, took the pipe of and found a 10p in the lower section and a 50p in the fatter section, both basically closing the pipe off, put them back on and away it went, nothing to technical really and no cost which is the main thing, filter maybe in a different place on yours but take the back off follow the pipe from the drum to the drain pipe and it'll be there, job done, Hope this helps,
Andy Linney, June 2008