Putting aside the fact that I think IVF is morally dubious to start with.
If we ignore those issues for the time being, I can see why they put in the original clause to require a father. It's better for a child to have 2 parents and in a single parent family it can be difficult to find the time to devote to the child whilst still earning enough to make ends meet.
That however, doesn't justify why the parents have to be one male and one female. OK, there are parts of growing up that a parent of the opposite sex to the child may not have experienced and so may not find it so easy to discuss with the child, but I suppose there will be many other people around who could help in that respect. So it seems sensible to allow same sex couples the same chances of treatment as mixed couples.
However, I don't see why that should be held out soley for female couples. OK, there are biological issues with an all male couple giving birth, but if there was a willing surrogate mother I can't see why they shouldn't be given the same options.
What I don't like is the idea of single mothers getting the treatment. I keep questioning my thoughts about this one, in case it's just a matter of traditionally families having 2 parents so this must always be the case. However, I think there's a lot more to it then that.
Yes, single-parent families are getting more common nowadays and I grew up in one myself. However, in many cases there is still a second parent figure even if they are one step removed. Parents seem to be the obvious primary role-models for a child and none of them will be perfect. It seems to me that the child might actually need both parents in order to compare and contrast these models during their development (that said, that's just a thought and has no scientific knowledge to back it up).
Also as role models, surely it would be most ideal for the parents to have a reasonable degree of independence and yet managing a household and bringing up a child can be too much for one person to deal with.
I don't know a huge amount about child development and parenthood, but overall it seems that a child needs mother and father figures in their lives (whether they are same or mixed sexes). OK, things like divorce happen and so this isn't always the case, but it seems irresponsible to create a life knowing in advance it is going to be put straight into this situation.