Are these maps generated by Strava? Although I have a Strava account I have never logged rides on there - once, perhaps.
I am trying to imagine where my lines might be and where there are sections that are not joined up. Given that we have ridden LEJoG, Lowestoft-Ardnamurchan, a couple of coast-to-coasts, I've done Southend-Market Harborough and York-Stowmarket, and have ridden all the way home from Sheringham, as well as Southend-Maidstone, Southend-Pontefract-Cheltenham, there can't be that many UK lines that don't join up. I think the Southend-Maidstone route will have caught pretty well all of my Kentish rides.
We had a Devonian holiday a few years back which included Totnes, Kingsbridge and Princetown, so that is probably isolated, there is some New Forest/IoW stuff which is probably separated, as well as the Solstice WARTIES that began in Castle Carey and ended in Pewsey. I don't think that the Surrey Hilly 50, which I have completed 3 or 4 times, is connected to anything else.