At Rye Harbour, there are two quite similar species of 'autumn colletes' active at the moment, ivy bee (Colletes hederae) and sea-aster bee (Colletes halophilus), also known as saltmarsh bee. Ivy bee (above) is the larger of the two, with reddish hair on the thorax and broad buff bands on the abdomen, while sea-aster bee (below) is smaller with browner thoracic hairs and narrower, paler abdominal stripes. The best way to separate them however is the plant they are feeding on (the clue's in the name), though I have seen ivy bees at least feeding on other species and sea-aster bee does apparently use other plants.
Ivy bee is a relatively recent arrival in the UK with the first records on the mainland in 2001. Since then it has spread rapidly north, with the northernmost records currently from my patch near the mouth of the Tees in north-eastern England (see here). Sea-aster bee is a relatively uncommon species largely restricted to the south and south-east of England and in contrast to ivy bee, which can occur well inland, it is almost exclusively coastal, usually on saltmarsh where the main foodplant grows.
* 'Bike' is an alternative collective noun for bees, along with 'grist', 'erst' and 'rabble'!