hi beachfront71,
The route that your aircraft took would have been dictated by the North Atlantic tracks which are generated twice a day by Shanwick and Gander in order to make best use of the strong tailwinds blowing from the US to Europe and also to best avoid them if travelling the other way! Since there is no radar coverage over the huge ocean, aircraft fly along these preset tracks and report positions along the track at set intervals. The controllers can then build up a picture of where all the aircraft are that are crossing the Atlantic.
As for flight levels, the optimum altitude that the aircraft would have flown isn't just concerned with number of passengers but other unseen weights such as extra fuel (the aircraft would most likely be carrying more fuel heading to the US due to the slower groundspeed and therefore longer flightime) and cargo in the hold for example.
Finally, the most likely reason for the fairly low altitude of 32,000ft on a relatively short North Atlantic run would be due to other traffic. Very often, aircraft are forced to fly at lower altitudes than optimum due to conflicting traffic hogging the skies above them!
Regards,
champair79