Having found the three sibling trackables together in one cache, I decided to hang onto them for a week or two until I could get to nearby Barcelona where I wanted to seed them into three different caches so that they could begin their race. I have no idea who thought to bring them to Spain from Scotland when they were racing to the north of England, but there you go - they've had a holiday. Now they are at the mercy of the next geocacher! It is not easy to find urban caches big enough for trackables, but I managed to plant them in an area where they should be easily found by travellers, so they should have a great chance of continuing on their adventures. Best of luck!
(P.S. Sorry that I haven't had time to take fun photos with them...busy time of life)