Thanks. At the moment I have it set up that the landing page has a default of London in the headline. Then if someone searches for an area of London, eg Westminster, the latter replaces London in the headline. The problem from an adwords landing page quality score point of view is that it stills shows up as London in the html, which is what adwords bot will read. It would be better if Westminster showed up in the html.
Is there a way to not have any town specified as the default in the headline, and have the search query town//district dynamically inserted into the actual h1 html? Like it does in the link I gave in my OP.