The local Presbyterian Church has a sign outside offering an Alpha Course. I'm sure I've heard of the same course being offered by the Roman Catholic Church. So is the Alpha Course a very general Mere-Christianity-type thing, or is it customised to each denomination, or are the two Alpha courses completely unrelated?
The Alpha course is extremely popular across the world and in many denominations. It originated in the Church of England, and it is exactly what you expect - an introduction to the core of Christian belief, Mere Christianity style. It is not specific to Anglican beliefs, and has been used by a huge number of churches of many denominations.
One of the key things about Alpha though is that it is intended to be more than a lecture series. It is key to the course (assuming it is being done properly) that it is done in a discussion framework. The lectures should be followed by a discussion in a small group, to which Christians and seekers are free to contribute. Ideally there should be food as well - the guidelines for running the course recommend it.
The only slightly controversial aspect of the course is that it does teach that the Holy Spirit may give supernatural gifts, such as speaking in tongues, to Christians. It doesn't claim that those gifts are essential, and it doesn't talk about more controversial gifts. Some churches choose to omit those parts of the course.
Some churches choose to modify the course in other ways, but the one you see is unlikely to be a different course. Ask whether it includes lectures by Nicky Gumbel - if so then you are getting the real deal. I would personally make sure that there is an opportunity for discussion as part of the course. In my experience omitting that misses the point.