I would say an definitive yes if planning on just doing Disney.
However,if you are planning on doing lots of parks,I think you'd be better offsite.
As a pp stated,cabs will soon mount up,added to the cost of all your tickets,would make your trip really expensive.
I'm in the UK also,and we've stayed offsite and onsite,but always had a car.
I would add,there are two main ways of booking your trip.
Either booking a package online/or with a travel agent.
Or,booking everything separately-namely diy.
You book your flights,accommodation and tickets all yourself.
If you decide to book a Disney resort,be aware,there are sometimes special offers,sometimes discount on the rooms,or
free dining offers.
However,free dining is never available on values-free dining starts with moderate resorts- so it can sometimes work out cheaper staying at a moderate than a value.