Question Author
Thanks, people... consider yourselves all Marked as Best Answer. Maybe there is some ornate trail to someone Mary and I both know, though how it came into the mysterious Joe Soap's hands I cannot imagine. Anyway, despite my yearning for friends, I won't be signing him up.
Swedeheart, NoMercy was pointing out on a travel thread the other day that if you look for a price on EasyJet, say, then go and check on Monarch, then come back to EasyJet, EasyJet's price will have gone up, presumably because they spot your IP address and guess that you've looked elsewhere and haven't found a better fare so they're free to raise their own. Maybe something like that is happening to your accounts.