If you both can obtain Senior Citizens Railcards, book in advance and travel off-peak you may find that you can get to many airports for very little money.
I realise things have changed over the last 2 years but I once organised a 3 centre trip to Italy for a pittance because we were flexible as to times and airports we flew from/to and took advantage of off peak travel and deals etc and were prepared to travel this end to get the right deal. You can get good deals on train bookings in advance.
I've never done this, but it might also be worth looking at a flight to somewhere else for a night then onto Lanzarote. You are both retired so you have the flexibility.
Ditch your cookies and also employ several email addresses. And also try more than one site. I did this on my 3 centre Italy trip and saved a fortune.