Hi, I'm a single mother by choice - decided to go it alone at 40, conceived when 41, gave birth to DS at 42. As someone mentioned up thread the beginning is very hard - for me it was the first 4 months rather than 6 (but then I only have one) - and also when I first went back to work when DS was 8 months. But overall, it's been brilliant, all my friends have been very supportive, and DS is the most amazing thing that's ever happened (both friends and my parents commented that I'm happier than they've seen me in years). Of course bits of it are very hard: it's especially difficult when I'm ill, I find.
Childcare is expensive but at the moment (not banking on this in the long run, as Cameron and his merry men may have plans on this front) I get quite a lot of help through working tax credits. I pay about 650 a month for full time at nursery (I work 4 days, but find that having an extra day allows me to change my hours if necessary - nurseries won't accommodate you paying for 4 but changing the days from one week to the next). But that's in the sticks - it would be more in London.
Big plus points for me include never having arguments about parenting choices, being able to be spontaneous - if we have nothing on and I feel like taking us to the beach/zoo at the drop of a hat, I can.
Having your friend involved as a father would be great, though. I think DS is beginning to miss having a father (we're getting lots of role-playing games about mummy,daddy, big brother and little brother at the moment and he's very cuddly with my male friends). Hopefully though we can manage to find a way through this stage. I also occasionally miss male input (see my thread on Dadsnet - DS has a medical condition such that a male perspective would be really useful).
Anyway, best of luck with whatever you decide to do.