This is something I am very familiar with - the best option is to have someone regularly check the incoming mail, provided you have someone willing and able to do this (a neighbour or a friend). I have a collection of envelopes which call for no action other than piling them up (direct debit stuff, statements, etc.), other stuff may need description/notification by e-mail and/or opening. The person will need a key to get at the delivered mail and he/she must be diligent/conscientious and reliable - if he/she misses something that may be important (doesn't alert you) then the whole thing can become a disappointment. It is a good idea to leave behind one form of ID acceptable to the Post Office in case something comes in that needs collection from them because if it sits around too long then it may be sent back.
Failing this, I think it is possible to come to an arrangement with Royal Mail that can get around the uncertainty you face