Is the PPL Flexible? I thought I would have had to be committed to a ground school for a certain period of time rather than just swanning in once every week to fly
Many many people have done it this way.
It's probably not quite so common for those with commercial aspirations to do it this way, because planning on making a career out of flying implies a fairly high level of commitment - so most Wannabes will probably do their PPL full-time (if they don't have other education or work commitments, or financial constraints).
But remember that the PPL you do (on a modular course) will be exactly the same as the PPL which thousands of enthusiasts an hobbyists do. I would guess that flying once a week is the most common arrangement - or at least one of the most common.
There is no requirement for formal groundschool for the PPL (although there is later for the ATPL exams). You can self-study from recognised text-books, or if you prefer ground-school you'll probably find that your school arranges classes - often on a weekday evening, spread over a few weeks, with one class per each exams or something similar.
Not being able to get to a flying school, however, makes things a little difficult, as you say.
FFF
--------------