Just to agree with just1moreplease - I'd read a fair bit of stuff on here about 'walk in' EPU's, but this isn't the case at UHW. They will only make an appt for you if a GP or other healthcare practitioner (MW) refers you. This is, btw, not what it says on their website, where it states patients can 'refer themselves without coming through another medical professional.'
They will also only see you if you have current and ongoing symptoms of possible mc (bleeding/pain). As per previous poster, a GP may say you have current spotting to get you seen, but that obviously depends entirely on the GP...
I'm very sorry you had a MMC, and I understand you are very anxious about this pregnancy, and why you really want a scan.
I really don't like saying it, but is there any way you can afford a private scan, to put your mind at rest? So sorry if that isn't an option, I really dislike '2 tier' care. The Spire hospital would do a scan - their early viability scan is £100, according to their website.
As just1moreplease says, I am sure you are/will be fine (I have no preg symptoms either, but we seem to be okay at 17 weeks and counting) - but I understand a previous MMC will be giving you a lot of concern.