In reply to Wee Davie:
Thanks for the ideas. To be honest, the very low budget solution of modifying, drilling holes etc., is of less interest to me - having forked out £430 for my phone, I don't mind spending a bit more on a tough case, but I do want a leash/lanyard on it, with a strong and reliable attachment point. In the near future I'm going to be 500m up steep ground, and the strength of the case won't do me much good if I drop the phone - it'll be gone.