Just checked my log book. Never got any of my solo XC flights endorsed in the log book. Also cant remember if I sent them the form which other airfields signed during the 270km cross country flight.
However what I did do is write ex 18A or ex 18B in the remarks so its pretty clear which solo flights count to the 5 hours solo XC. Maybe this is where you are falling down. If it doesn't include a land away its not immediately obvious it's solo CX so CAA don't count it ?
Mind you that was 10 years ago and I had to apply for a JAR licence using a CAA form - all very confusing. Maybe as much for them as me.