UK.jpg

Reliability graph produced by ACE-HF
This shows that to work the UK-based stations from within the UK, 80m (3.5 MHz)
is probably your best bet. However, as D layer absorption builds up during late morning
you may find signal levels dropping off - as shown by the lower yellow
band. The next band up (excluding 5 MHz) is 40m, but this could be
marginal as well as the critical frequency (NVIS) may struggle
to get that high. So, make sure you are on 80m early and after 4pm.
Around lunchtime by all means try 80m, but also look at 40m too.