Yes, they were contrailing. Sorry, always have called them vapour trails... Approx route from Midhurst, NE over London, probably fairly close to over the top of Heathrow.
Trails were very short compared to the other well developed contrails which I've noticed throughout the day, which presumably suggests they were either close to the minimum altitude at which trails were forming, or perhaps a bit higher than most other traffic?
They didn't appear on FR24.
May well have just been a pair of vertically separated airliners - perhaps a couple of Flybe ERJ190s heading up north from Jersey, but there was something about them that suggested a pair and possibly of more interest. So if anyone saw them and got a positive ID, I'd be most interested to know.
Reminds me that about 35 years ago while at school not far from
Midhurst, I saw a couple of contrailing fighter formations. One was heading south between Woodley and Midhurst and later turned out to have been a batch of F-5s on delivery to some air force or other. The other was routing Midhurst towards Dover and was a group of four fighters and a four engined aircraft, I've always assumed a KC-135 accompanying a detachment of F-4s or F-15s from the US to Germany. I was in a French class at the time and couldn't take too much notice!