... and spend some time reading Peter's trip reports, they are a mine of knowledge. Suggest getting a full subscription to Meteoblue for weather too (you can just do it for a month if required). If you are getting a 2000/3000/4000ft cloud base at LESO/LEBB it doesn't mean you are going to get across the mountains VFR. Depending on the time of year you are looking to go they can collect a lot of cloud... If you are used to flying relatively short trips in the UK the weather planning is a little different to when crossing half a continent.
With two of us with IMC ratings we got out of the the UK on a Y plan and were then above a solid cloud base all the way to Rennes, which cleared to CAVOK as forecast to arrive at Nantes. We then got a lucky break and the following day was CAVOK allowing us to get down to LESO and then continue into Portugal where it got a bit convective, but pretty much exactly has we had expected, so we managed to slip in to our planned fuel stop about 30 mins ahead of a cell, waited a couple of hours for things to clear and routed on to Evora which was the final destination.
The return was a totally different kettle of fish and we waited a long time before we were able to depart VFR in Spain and have cloud tops over the mountains low enough for us to be VMC on top over. This cloud was all sitting along the mountains in the North of Spain and there were many days where it went up too high for us to get over not having the sort of equipment Peter does. Once a couple of miles out over water, all was CAVOK again!
Meteoblue was VERY useful for predicting the tops, which you don't get from a TAF/METAR or low level forecast. Getting a login for the the French weather site is quick and painless, but despite applying a month or so in advance I didn't get access to the Spanish or Portugese ones until after we got back.
Go enjoy, just spend some time on the planning. Maybe we did too much, but we did at least have a very enjoyable trip with very few surprises that weren't weather related.