I mean that the workings of FPTP make 90% of the votes pointless because they make no difference.

No idea how you reach that figure. As above the defecit in achieving majority rule (51%) is presently 17%. Under the Tories previously it was 7%.

Generally 30 to 40% get what they voted for which is usually Tory.

As commented elsewhere voters are creatures of deeply ingrained habit. They vote for for the parties their parents did...as though it defined part of their identity. I've mentioned before the lady in some rural town a few years back who was a Tory voter but agreed with all of the prospective policies put to her and was most surprised to find they were those of demonic Cornyn and Labour.

-Yet you can bet you last pound that at the GE she still went on to vote Tory.

There is an idea behind this that are merely voting for stability and continuity..it's in the name: "Conservative". Unfortunately for these voters the party changed under Thatcher to something expousing radical change instead.