I flew MAD-EZE last year with IB in J.
We had the old business seat on the way out, the new one on the way back. Both are lie-flat.
Strangely, the old seat is more spacious, and I felt more comfy in a squishy sort of way. Actually quite liked it for a daytime flight. The IFE is pants, though. Next time - but I think IB have now just about finished getting rid of it - I might treat myself to an ipad and take my own films.
The new business seat is nice, but choose the centre pair in the middle if a couple. I made a mess of seat choice and we ended up with two aisles. You get bumped into by the corridor traffic.
Our choice for the next flight - to PTY and MIA to MAD were the window seats - one behind the other. They are a really nice private space, especially for one. (with the PTY flight, we then found ourselves in old J - so were sitting apart. But someone kindly offered to swap seats. Again, this 340 had the second smaller cabin at the rear - didn't like being in the front row of that and the back row would be noisy near economy. So choose row nearer the front in case of getting "old" J)
To sum up:
Take Easyjet from Liverpool to MAD. Stay the night. Great daytime flight. Much better avios avialability, lower YQ - make sure you have an IB+ account for 90 days etc - and choose seat and row carefully.
And enjoy the Pedro Ximenez 30 year old sweet sherry. It is nectar!