Please could you tell me the difference between these and is there anywhere that will automatically email these to me for selected stocks?

Regulatory news was deregulated in April 2002.

Previously the sole preserve of the LSE's RNS service, there are now some 6 other primary information providers (pips) including PR Newswire, Hugin etc. Pips in turn release regulatory announcments to the secondary information providers (sips) such as AFX, Reuters, Bloomberg, where additional content may be added.

So the pips provide the regulatory news to the sips and then the world and the biggest pip with about 85% is still the LSE's RNS service, which has sensibly kept it's RNS name.