Bill.. I have been watching the skies avidly as an aircraft spotter since I was about 6 and I am now 66. I was an air traffic controller for 35 years, during which time I watched the skies with my eyes and with radar. For 31 of those years I worked in the busiest UK airspace. With that in mind I'd jujst say that I do not accept that "chemtrails" exist in UK airspace.
Contrails have been around as long as I can remember but they are not always visible. It all depends on the atmospheric conditions and the altitude of aircraft so there may be several days at a time when contrails will not appear, but the aircraft will still be there.. The various lines usually follow published air routes which may be seen on easily obtainable aeronautical charts. Remember that commercial and military aircraft are usually under radar control so they may be directed off the usual "straight-line routes" if necessary, thereby producing curved lines.
There is nothing at all unusual about what you have seen.