So when applying for the foundation posts would the intercalated degree count in your favour against those without it? ie meaning you're more likely to be accepted to a post rather than someone without the intercalated degree?
Yes - and a normal intercalated BSc (year out) is worth more than the BMedSci, and an intercalated masters is worth even more. It all adds points into a scoring process that also depends on other things including your rank within your year, how well you do on a national exam called the Situational Judgement Test and how many papers you have published in a medical journal (which intercalation helps with too).
Intercalation also helps at other points in your career - not only applying for foundation places. For example, for the next step of training after foundation training (core medical, core surgical) a 1st class intercalated BSc is worth the same number of points as a PhD.