Unless you really have a "thing" about having a filter, the simple answer to the filter issue is to remove the filter part (the white bit) from the end cap (the clear bit) and just use the end cap as a blanking plug, doing away with the filter completely.
Unless people change the filter religiously when they should, they can cause more problems than they supposedly cure.
Most of the filters I see in the course of my work have not been changed as often as they should, usually noticeable by the green algae on the inside!!
UK tap water is probably the safest water in the world, and just ask yourself, do you filter all the water at home?
We have been camping and caravanning for over 40 years and have never had any problems with site water, here or abroad, and never use a filter.