Flying days in the UK were more frequent than I expected, especially if you can be flexible and do mornings and evenings. Often, you can watch low pressure systems and fronts go through and know that there will be an area of calm before the next one arrives.
Spain looks fantastic, especially beach flying, where light winds are the norm and even a breeze on the beach tends to be less gusty.
Obviously Southern England is better than the North in that respect, but there are many northern PPGs who enjoy the sport.
One thing to be aware of is that if you train in the easier Spanish conditions,, you may find it quite difficult in UK conditions, though if I had my time again (knowing what I know now), I think I would have done a course in Spain at outset.