Trying to save her husband's dying gift

Just had a very emotional conversation with Mrs Pritchard who approached Tailwaggers Club Trust for some help.
Having heard the full story I thought I'd open this one up as many brains may help untangle this one...
Mrs Pritchard's husband was diagnosed with terminal cancer and they had not long lost their beloved dog. He didn't want her to be left alone after he had passed so set about finding a new dog. They visited rescue sanctuaries but her husband couldn't find, "the one".
It was when they met a Sheltie that they realised this was the dog for them. They visited a breeder and Jack was found. A beautiful tricolour dog.
There was a lot of sadness in Mrs Pritchard's life. Not long after her husband died her ex husband was found to be terminally ill too. She nursed him and took in his dog, an elderly Corgi. Then Mrs Pritchard herself fell ill with Ovarian cancer.
Jack went in to be castrated, but shortly after coming home he couldn't stand up, he was falling over. His back legs didn't seem to work.
Lots and lots of tests were done at the vets but nothing could be found to explain his back leg weakness.
Jack appeared to get better, although he always did have a jippy tum. Mrs Pritchard put him onto James Wellbeloved and things seemed to calm down. 
Then two weeks after his booster vaccine, Jack had some fits and was foaming at the mouth. He was hospitalised and more tests were done and the vet seemed to think the earlier problems were related and it could possibly be IBS.
Mrs Pritchard is a pensioner, a widow. The vet bills are massive and the problem as yet unresolved.
She has already cashed in an ISA and is now looking at extracting some equity from her house to pay the vet bills.
Jack is currently out of hospital and urinating every hour - which means she is getting up all night to let him out.
Jack means the world to her and she is worried sick about him. He is currently on prednisolone, zitac and netoclopranide. He has lost a lot of weight and his coat looks dull and seems to be changing colour.
She feels her vet couldn't try any harder, he wants Jack back in for more tests. He wants to look at possible Thyroid problems next.
Her total vet bills to date are close to £4k and rising.
I have suggested she might wish to consider a referral to a holistic vet - just to see what the alternative world can suggest in this case. Looking at perhaps changing the diet as if this is an extreme form of IBS then maybe a more simple diet may help. And also to try to reduce any further challenges to this poor dog's immune system by looking at blood testing before further routine revaccination.
It could just be coincidence that both health crisis have been after surgery and vaccination - but could this be an autoimmune condition that is flaring up after any challenge?
Money is very tight and after all the money spent to date Jack remains very poorly and without a clear diagnosis.
Mrs Pritchard says she is open to any logical suggestions and feels very worried for her beloved dog.
She lives in Cornwall between Plymouth and Tavistock.
Can anyone recommend a nearby holistic vet?
Mrs Pritchard said it had been lovely to talk to Tailwaggers as it has been so hard going through all this with Jack alone, but that she will go to any lengths to save Jack. She has every confidence in her vet, but would not like to leave any stone unturned.
I will set up a JustGiving appeal on the Tailwaggers blog for Jack as no matter what Mrs Pritchard who receives pensions credit is struggling with the bills she already has.
Anyone got any ideas? Anyone in Shelties seen or heard of something similar? Mrs Pritchard says that the stud dog owner has had some colitis problems in her dogs. Mum is apparently of Russian descent, but the breeder has moved so Mrs P can't contact her. The pups were reared on raw mince so it seems likely the breeder was a raw food feeder.
I've set up an appeal for Jack on Just Giving.

The excessive urination is probably being caused by the prednisolone - this
is a common and well recognised side effect of steroids.  It may be possible
to continue with the prednisolone but at a much reduced dose.
As your correspondent Queenie says, there may be a Burns food which is
suitable for Jack.  All our adult foods are very digestible and low in fat.
They will not cause irritation to the digestive system.  The feeding amount
should be less than the recommended amount and should cost no more than
40-45 p per day and possibly less.  Mrs Pritchard should not attempt to
manage this on her own; she needs to work in consultation with the Burns
Nutrition team.
When we decide what food to go with we would be willing to supply her with a
free bag to try.
John Burns BVMS MRCVS
Burns Pet Nutrition