I suffered from this for 11 years following a simple ear infection. Kept going back to the GP and then ENT specialist who basically said I would have to live with it and it would go on it's own possibly but could come back at times. After 11 years I was so fed up I asked for a second opinion, GP was not too pleased with this but sent me to the ENT department of a different hospital (with the sort of attitude of 'They won't find anything we haven't already told you but just to keep you happy....' type of thing.)
I went to the other hospital and the ENT department did an afternoon of different tests and straight away diagnosed BPV and said they could sort it out in no time. I had to undergo something called a Particle Repositioning Manoevre, which took probably 10 minutes and involved them turning my head into various upside down and sideways positions to relocate the fluid in the ear (which apparently had some deposits floating around in it which were landing on the balance mechanism causing the dizziness when turning over in bed or in my case when bending down) into canals which had no affect on balance.
(A bit like one of those snow globes that's how they described it!)
It was brilliant, just had to be a little careful for about a week after, but then the symptons had gone.
Apparently at the time not all hospitals were aware of this treatment and didn't have staff trained to do this manoeuvre.
I was told that it could be cured for good or could return at a later date, but I was given a direct dial to that department and at the first sign of any problem again I could ring and make an appointment to have that manoeuvre done again within a day or two. Over the following year I probably had it done a couple of times, but since then I've been fine and that was over 10 years ago. (I still have that number in case though)
I can't believe I suffered that for 11 years when there was a simple, painless solution out there.
It's worth a try - good luck!