Flight Delay - Compensation

JenniStokoe

I am looking for some advice.
My family and I flew with Thomson Airways Limited in 2009 and suffered a 24 hour delay (Palma, Mallorca to Manchester, UK). I contacted Thomson in the UK with regards to compensation but received a letter claiming 'extraordinary circumstances'.
Not happy with their reply I contacted the AESA in Spain.
I have just received a letter from the AESA stating

'AESA considers that the reason for the delay invoked by the company would not constitute extraordinary circumstances pursuant to Regulation (EC) No. 261/2004. Accordingly, the air carrier should pay you a compensation for the amount of 400 Euros per passenger considering the distance between Palma & Manchester is 1.581 KM.
We inform you that Regulation (EC) No 261/2004 of the European Parliament and of the Council of 11 February 2004 shall apply without prejudice to a passengers rights to further compensation. The compensation granted under this Regulation may be deducted from such compensation. In this case we inform you that the convention for the Unification of Certain Rules for International Carriage by Air (Montreal Convention of 28th of May 1999) establish that amy action for damages contemplated in Article 45 must be brought, at the option of the plaintiff, in the territory of one of the States Parties, either before a course in which an action may be brought against the contracting carrier, as provided in Article 33, or before the court having jurisdiction at the place where the actual carrier has its domicile or its principal place of business.'

Can anyone simplify this for me and let me know if I am able to pursue Thomson for a claim in the UK and how best to proceed.

Many thanks in advance