I have taken a chance that the prices wont come down and booked Christmas (22/12 - 1/1) for £175 with a reserved seat both ways. Also Easter (Sat to Sat) for a similar (lower) amount.
I hope my faith in the "school / big holiday - book early" mantra will pay off ! Just about held up for this year and I didnt loose out - but there is always a chance it can go wrong
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I know its a long way out but I think it will be worth it in the long run - even though they are holding my money for so long