Thanks everyone.
So I talked to an out-of-hours doctor on the phone last night, who said it was too early for a scan or anything and I would have to just wait and see. A couple of hours later she called back to say that actually, as I had clomid, I she could try and get me a scan at the local early pregnancy unit. I have an appointment early Monday.
I also rang my fertility clinic to ask about a private scan, in case they had something available today, but they don't have any scans until Monday either, so I am going to stick with the NHS. The private guy also said that 20% of women bleed in pregnancy, so it is not good, but not unheard of either, and that it is a good sign that I don't have any pain. He also reckons that I could keep bleeding all weekend - it would still be hard to say what was going on either way.
I thought I might have stopped bleeding last night, but there was more blood this morning. It seems like the very start/end of a light period and is getting darker, but not heavier. I have also lost the feeling that I 'just know' that I am pregnant, but that is a very vague thing anyway.
Looks like I will just have to settle down to a weekend of uncertainty and rest.