All licence applications cost the same in the UK, regardless of what you apply for (or to be more exact: the cost scales with the size of the venue according to fixed bands related to "business rates" valuations).

Licensing conditions are actually entirely fluid and negotiable between the applicant and the local council, who act as the licensing body. Not only with regards to opening hours, but also to all sorts of weird and wonderful additional terms. In practice when it comes to opening hours, a lot of pubs and bars apply for (and are granted) licenses quite a lot later than their actual intended closing time, as it gives them leeway to open late for special occasions without the need to apply for a temporary extension, and gives flexibility for "lock ins" (i.e. continuing to serve customers after they'd normally have shut up shop).