Upvote:4
The main concern of the UK Border Agency seems to be to ensure that your visa is only used for visiting, but not for taking up de facto residence in the country.
Unless there is a note on the visa that says something along the lines of "may only be used to renew passport", or otherwise restricts your entry to a specific purpose (see #6), you can enter the UK multiple times as a tourist. Both touring the UK and renewing your passport seem to me valid reasons of spending time in the UK that would not be considered akin to taking up residence.