Much of above true, but...
I've a share based at Elstree. Much of the above criticism is true, from unfriendly radio, to tightish parking and sloped runway etc.
I did a quick half hour trial there ten years back, then being fortunate enough to have saved enough to pay in one lump, I did an all-in PPL course in Guernsey - and I KNOW the "eat, sleep, dream flying for three weeks" worked for me. But it may not for everyone, and you'd have to get the money / time off work etc.
And so what I'd say is, yes, convenience is VERY important, all the more so if you plan to spread the course out over months. And in that case, Elstree may be closest etc.
One thing I would comment on is that Cabair and Firecrest are the only ones able to fly "normal" circuits at Elstree, (If you can call the 3 different circuit positions 'normal').
But there are other, probably considerably cheaper, ways to learn at Elstree. After getting my license in Guernsey, a friend introduced me to Lion Flying Group based there, from whom I hired Cherokees etc. But they also have very experienced, qualified CFI, and currently, I believe, at least one C150 and one C172, and have successfully trained many PPLs.
But there is one other factor affecting their training. They, as do other owners based at Elstree, now have no option but "Four mile Final" type of, er, massive "circuits" (if you can call them that), be they on 08 or 26. So what might be, say, an eight minute circuit with Cabair, may be a 15 minute circuit for others! Which may ease the time pressure a bit when it comes to circuit practice, (but of course clocks up more tacho. time/cost per circuit.