If you're quick and have time, interrail tickets are on sale for a 25% discount until tomorrow. 10 days in 2 months first class travel for a bit over €400(less for under 27's or over 60s, and free for under 12s), plus £38 each way on the Eurostar with a (very) light meal and wine included each way.
Works better for Germany than Spain or France because there are supplements on the fast trains in France Spain and Italy, but you could take in several games in different cities over a couple of weekends. Lille would be a good first stop, then maybe Anderlecht in Brussels or Cologne. Or even Ajax and wear a Boro shirt to watch Chuba!