>>She has always had her eye on my pension and once said before we went our separate ways that if we separated it seemed silly to divorce as she would miss out on the pension! Bizarre but she said it.<<
There is nothing bizarre about that. From her point of view it is perfectly rational. If you were to die before her while you are still married she would almost certainly benefit automatically from your pension as a surviving spouse. If you are divorced at the point of your death before her then she would get nothing from your pension.
You may or may not want to go along with that but if you want anyone else to benefit from your pension after your death (if that is possible) then you need to get a divorce. Bearing in mind you have been separated for six years the marriage is obviously over. Normally it would be sensible to get a divorce under such circumstances. Do bear in mind that if you die while still married to her she may well have claims against your estate and not just against your pension. Your wife may be keeping quiet about this part but you need to be aware of it.