Hi - we had a water filter tap fitted in our previous flat when we had a new sink put in. It was a Franke Mini Triflow and was separate to the main tap. I definitely preferred the taste of the filtered water, I am not that keen on London water.

Our plumber fitted in quite easily. However you do need an extra hole in the work top to fit it into. Much more convenient than those jug things and probably not more expensive in the long run because the filters last for ages.