Dusty
Taking the responsibility for rescuing a neglected horse is a very significant committment.
"Falling in love with Fell pony" is understandable in a young teenage girl. I have found that mature ladies of 40plus are usually more reserved in declaring their affections. However in a sense your words help set the scene to we readers of a post over the internet. Fells can be cute.

What I have been trying to say - in my aged male speak - is that this project calls for considerable expertise - the sort not always found in books and certainly not in 5 line answers over the internet - even from well wishers.

Can a mature Fell be taught manners? - in theory yes - but there must be a question mark about whether the animal is too independent. Presumably if you knew more about the pony's early life you would have told the Forum. The early years in a horse's life can be the most influential and you will have difficulty in erasing those memoriies - good and bad - which this pony has experienced. Noone on this forum can make a judgement as to the trainability of a horse without
getting close to it, touching it and working with it - certainly not a valid judgement for you to have to pay the price over the long term for.

From my point of view - if you are prepared to give the horse a good home - once you learn what that is -it doesn't matter whether you ever ride the animal, it will be better off with your giving some tender loving care than it will ever be standing out neglected in some field. But the knowledge any long term horse owner and rider has acquired doesn't come easily - it takes years to acquire about not only what to do but what not to do. The big risk with you is that of your become a doting owner and spoiling the animal.
If it really is cute and crafty it will run rings round you.
If your land is too lush and you over feed it, then it will get laminitis.
And just in the handling of a stubborn, ill trained independent moorland pony on the ground you might get hurt. Fells can be tough little devils.

If you have some local experienced help then maybe go ahead - the pleasure from owning a horse goes way beyond just riding it. But please don't take the creature on and then dump it in a year's time because you can't cope. A pony can live over 30 years.

Incidentally - few other suggestions:
Get the pony examined by a well respected horse vet - legs, feet, back, teeth, movement - the works and take careful note of what the vet says.
Find a local Pilates exercise group - you'll need to be strong round the centre core area - stomach muscles, lower back, thighs - with flexible hamstrings and calves.
Buy a hard hat and a body protector.
Cancel all holidays, re-arrange your daily schedule and get ready to spend a fortune on tack.
And as a mature lady, don't even think of falling off.

If you really want to join the international horsey club - then do so - just make sure you pick the right horse for you and your circumstances.