Yes , Giulietta is totally right, its not just Biscay but the passages at Ushant, Cape Finesterre and Gib that can all be tricky on occasion. You've enough experience to hack this, but not yet as skipper.
Can you find an experienced skipper to help get you there? Or is there someone else you could sail with down to Spain for the experience, do an RYA Coastal Skipper course for the navigation and boat handling, take time to build up yacht management expertise, then go next year?
Another possibility, if your yacht is not above 5ft draft and the engine is reliable, is to take the mast down and motor through the French canals to the Med. Slow, but safer and interesting in its own right.