I've recently improved the keys to Cantharidae and posted them on the website at https://sites.google.com/site/mikesinsectkeys/Home/keys-to-coleoptera/cantharidae. Using these you should be able to have a go at identifying any British species in the male sex. The species of one of the genera (Malthodes) are very similar but have very good characters in males.
I have also made adjustments to the key to Chrysomelinae to accommodate Paropsisterna selmani - a pest of Eucalyptus which has fairly recently been found in Great Britain.
The members of family Ptiliidae are mostly very small and include our smallest species, the recently discovered Baranowskiella ehnstromi. The key posted at https://sites.google.com/site/mikesinsectkeys/Home/keys-to-coleoptera/keys-for-the-identification-of-british-ptiliidae should allow you to get some way with identification but you will certainly need a good microscope with good lighting. Happy identifying and do let me know how you get on - positive or negative points.