Sorry just picked up on the ref mentioned. The simplest solution would be some kind of wedge cushion but I would suggest you consider getting a full assessment, it is actually quite a complex problem and not uncommon, the solution can differ according to the root cause. An assessment would also give the best way to get a solution that will last. The DLF is a good source of neutral information on products they also have information and fact sheets which may help you if you want to find out more and/or don’t want to take the assessment route - if you have a decent shop nearby they can be a useful source for info and advice but you want a shop that wants to help and not the hard sell so be alert and don’t be rushed into a decision. Hope this helps a bit more.