If it includes taking it all away it sounds very reasonable to me. My neighbour paid �120 last yr for the same job & it was the cheapest of 4 quotes. (Derbyshire)
It's best to have a few free estimates to compare before you decide.
if it does include taking away I would say that was very cheap, just make sure they have all the insurances, I know a tree surgeon who took down a 45ft tree few weeks back and it cost �450, and that was reasonable. including cutting it into managable sizes for chopping into logs, but no clearing away.
As the girth of a leylandi is not too great why don't you remove the lower spindly branches up to the height of about 8', then tie a rope to as high as you can reach and after employ a local DIY man to cut near to the base. Even if the tree was to topple in his direction because you have removed the lower branches he would be relatively safe.
hi there i am in the same line of work and yes if they are taking it away thats cheap it will cost them half that to dispose of the tree unless they are diddies lol. then it will be at the side of the road. and on a serious note if that happened and the police could prove it came from your house you would have to pay again for removal and disposal.