personally i dont think early scans are a great idea. there is a reason the NHS scan is at 12 weeks. more often than not instead of reassurance they end up worrying people. having a scan earlier isnt going to tell very much- when baby is very small you might not be able to see very much- then that will create even more anxiety - and then the repeat scans needed etc- also if worst come to worst and it wasnt progressing as expected would you really want a private scan person informing you of that? I mean it depends on the person but i know NHs staff are professionally trained to give bad news and counsel you and offer further support, but who knows what youll get with a private provider.
Also no scans are 100%- it depends so much on where youre at /position/and the person doing the scan- there have been a lot of cases where on early scans ppl have been told there is no baby etc- only to find out later it was wrong
Its every individuals choice as to what to do but I would rather just pray and wait patiently for the 12 week scan - either way an early scan isn't going to change the outcome.