I know I'm not a single parent, but I have faced a little bit of my DH being away: in his case it was for (bad language) fishing trips, rather than work, which I can stick better. Both are only for about a week, but the principles will be the same.

Get out and about. Go out to a coffee morning with a creche and have "me time" that way - it's only for an hour or two, your kids will have new toys and you will have adult time. (I have only just started to take this advice myself, we don't like leaving each other!)

Make new Mummy friends at playgroups or mum and toddler groups.

Have girlfriends round to yours in the evening, post children's bedtime - their OHs can be left with the babysitting duty.

HTH!