Depends on how many trees and the size of them.  The manual pruning saw on a pole works well (only cut on the pull stroke) for anything up to about 3 or 4 inches diameter.  The pole chainsaws are readily available but if you're going to use it for a number of years I wouldn't bother with anything from Bricorama and the like.  There's a Huskvana shop near the town side of the Millenium bridge or you could try the Sol D'Ebre co-operative or Hierrez just up the road.  Expect to pay about 120 for electric, more for rechargeable and 2 -300 up for petrol.