Sorry if it has been mentioned but you have to consider how you are being charged as well.
Block time, from start of taxi to stoping on your return could be expensive at a busy airport like Liverpool if you are sat at the hold waiting for a stream of Ryanair and Easy jets to land. You may also become quite good at flying in circles waiting for a gap in airliners to be able to land.
I would like to see charges at big airports based on Airborne time or Airborne time plus a set amount for taxi.
I seem to recall at East Midlands where I both learnt and was an instructor it was airborne plus 15 minutes.
If you want to become an Airline pilot is starting to learn at a big airport an advantage? Possibly so but the way you operate alight aircraft at somewhere like East Midlands is very different to how airliners are operated. Flying out of East Midlands was perhaps a disadvantage in the early lessons but did lead to confidence in dealing with Controlled airspace and ATC as I advanced through the course.
When instructing at a small airfield I would encourage my students to visit East Midlands as they neared the end of their PPL or just after qualifying, some PPL's from the sticks seem to just want to stear clear.