This is what I call a Shorty, around 50 pages and it was also a freebie. It takes place after Screwing the System, but can be very easily read on its own. And it should be because it's a fabulously fun little tale!
There's some BDSM, but it's happy BDSM and I love Jo for that. Cosmo is a very bratty, very lovable young sub and Alasdair is his older, experienced dom and most probably love of his life. :) Cosmo's birthday is coming up and thereby hangs the tale. It's a fun, funny, sexy, affectionate romp and just the thing when you're looking for something light-hearted and happy.
The title is a bit of a pun, but you may have to be from the UK or aware of UK slang to get it.
Anyway, the first book, which I've not read, is going on my To Acquire list!