What's army life like if you are in a long term relationship with someone outside of the army?

This varies significantly from person to person. Often it will depend on how flexible your partner is. You may move around a lot, and it is useful if your partner can move with you. If you are married you are entitled to a house provided by the Army at a reduced cost, if you are not married you can still apply for a house but you may not get one if there are none available.

Personally, I have found it ok, but my partner is happy to move with me and doesn't mind too much if I am away abroad for months at a time. It is usually harder being the person left at home than the person who is away.

6 months ago I saw my partner every day, at the minute I see him at weekends, there has been times in the past where I have not seen him for months.

While you are in the UK and not on exercise you will rarely work weekends (depending on your role), so if you are living apart, you will be able to go home then, and most units often let people leave early on a Friday to make the journey easier.