Problem with hearing aid and sunglasses!!

I'm a new wearer of NHS hearing aids and am having a couple of problems which I hope someone can help solve.

My aid on the right ear fits well with no problems but the one on the left keeps slipping completely off my ear.  I just cannot get it to sit properly.  What, if anything, can I do to rectify this?

And

This sounds odd, but as a spectacles wearer I prefer the overglasses sunglasses to the clip-ons, but once again the problem is the left ear as the minute I put the sunglasses on my hearing aid slips.  The young lady at the hospital clinic did have a look and the problem would appear that my left ear is much flatter against my skull than the right one, which means there isn't as much room for glasses + sunglasses.  This may well be the reason why the aid keeps slipping off anyway.

I did ask her for advice but was greeted with a shrug of the shoulders and nothing else.  Fortunately my hearing loss is such that whilst on holiday recently I didn't wear my aids at all,  but this really isn't the solution.

I can't believe I'm the only one who has experienced this and hope someone can help me.