How do I get to the pump filter on Hotpoint WF860 washing machine?

Water is coming from underneath my washing machine. I have had this problem before and the cause was colour catcher sheets which had got stuck in the filter. My engineer advised me to put them in a wash bag which I have been doing, but now got a new leak. I am sure something has got stuck again but did not watch what the engineer did so don't know how to access the pump. Can anyone give me 'an idiots guide' to doing this.