Do you know where he's deploying (the general area, don't put specifics)? Not familiar enough with Army ops to know where this might be, especially for 8 months. This will affect how you can communicate, including the time difference. In some places use of personal mobile phones is restricted, but phone cards are issued to use landlines. Other places there will be use of emails, Skype etc. There are also 'blueys', which are free email letters that you can pick up at the post office, and now an online mail services. You might also have the opportunity to send 'care packages', parcels with toiletries, magazines, sweets, just little gifts and practical items that are always appreciated. It is doable, but takes a lot of patience, and allowing for the other person being busy and sometimes absolutely knackered from work! Best thing is to talk with him, find out more about his job, how often he might be away (I would think there'd be a reasonable time back at home base after an 8-month stint) and where his job could take him in the UK, as he won't always be in one place. And ask him about how to keep in touch whilst he's deployed; tell him you'd like an address to post stuff and how would it work with phone and e-mail. His reaction to that might tell you how he views the relationship.
I'm ex-RAF, as is my boyfriend, and when we both served we spent a lot of time apart because of our day jobs, let alone deployments; longest period was a year. There's Forces families that manage it, too, with someone back home working, looking after children etc, so it's common, though I know it's scary when the relationship is new and unfamiliar to you.
There's also an Armed Forces forum (under Careers and Jobs) where this kind of thing has been discussed; if you post on there, read the security rules and don't give too much away about the situation.
Been through this, so happy to chat further!