Having done this before though not in the UK I would suggest just putting hold on your mail delivery.
Royal Mail advertises the Keepsafe which is very similar to the US Post offices Mail Hold Service, the only difference being that Keepsafe will cost you. This way your mail is held for up to 66 days and then made available to you.
You can try to set up the Redirection, which will deliver your personal mail elsewhere (including overseas) but this usually is reserved for the moves rather than a short term travel
As far as mail scanning system I would rather avoid those services since anything that goes online you should consider that no longer being private correspondence but if you don't really care about such matters there are multiple services that seem to offer this for you UK Postbox may be one of them (I am sure there are more but I'm not gonna display the entire Google search page)