There are several companies such as Key Cafe, who store keys and you can arrange for guests to pick up/drop them off after the stay.
The downside is you have to rely on the guest picking up during opening hours, remembering to drop the keys back after and the associated issues and so on.
There is a similar business that links up local corner shops/ newsagents registered with the business to host keys for guests to collect/drop off- again with some room for logistical issues.
You could work with an Airbnb management company and just use the guest meet/greet service for check ins when you’re not available- then at least your guest is seeing a friendly face and not having to hot foot it to a key cafe or corner shop! (If any of the above services are available in Manchester I don’t know)
Or you could get a co-host in Manchester who could manage the check ins you can’t :-))
Or you could do what I have seen some hosts do in New York and attach a padlock keysafe to a nearby railing (not ideal, and I’m joking here!)
