Thanks for all the replies.
We are visiting the solicitor in person next month and will be establishing what work has been done to date. We cannot see 80% of the work and will discuss why the contract relating to fee's did not have stage payments listed, particularly when the contract for the house was on this basis!
Feedback from others is that those who have made some payment of solicitor fee's have not paid more than 50% and on this basis we don't intend to pay the 80% invoiced.
The more we get into the purchase, the more it feels like the Spanish love to have our money sat in their accounts!