Your post is difficult to understand but you seem to be saying that your family paid land purchase annuities and that there is a record of this, however the land is registered to someone else.
Also your grandfather may or may not have purchased the land in 1910 or thereabouts and you're wondering if a solicitor was involved and if so, how to find out. If a solicitor was involved more than likely the title would have been changed into your grandfathers name. It is very very unlikely now that you will find a file in some solicitors office from almost 100 years ago that will show a contract was made or money paid over. Indeed it was quite common back then for people to make informal agreements, pay over money and never change title.
As I said in my previous post it a squatters rights application is more than likely the way for you to go now and you should take solicitors advice on it.