Different aeroplanes have different take-off and landing distances - the reasons for this are numerous, but thrust, weight, braking efficiency, high wing versus low wing are all players. It's then factored for wind, temperature, altitude, water snow or slush on the surface, (occasionally) length of grass and a few other issues. There are also mandatory safety factors that have to be applied for some kinds of operations - including commercial passenger carrying.
For public transport operations it's mandatory that a pilot confirms that a particular runway is suitable. It's highly unlikely that two different aeroplanes, at different weights, will come up with the same required runway length - and if they come up with values either side of the actual runway length one will accept the runway, and one won't. This is normal, and nothing to worry about with regard to either operator.
Having said that, you describe a missed approach - that could be for many reasons, but any pilot MUST fly one if he or she isn't 100% happy that he could perform a safe landing. It may well be that the Avro's captain just wasn't happy with the approach flown given the poor conditions and decided to go around and try again.
Regarding your red/green colourblindness, there's absolutely no reason this stops you flying, it just stops you holding some types of licence.
The BGA glider pilots medical, the CAA "pink chit", and the NPPL medical all will permit a pilot to qualify with this problem - there will be a restriction on flying into airfields that use coloured signals for communicating with aircraft, but I'm not sure there are any of those left anyway.
So, as a private pilot you could fly gliders, microlights, simpler light aircraft, motorgliders, balloons and gyroplanes. You'll probably be unable to get complex, IMC and night ratings for light aircraft flying, but that's not a huge loss for recreational flying.
If you wanted to later fly for a living, you could certainly become a microlight or gyroplane instructor and (I may be wrong on this last, if so I'm sure that somebody will correct me), a commercial balloon pilot.
G