Pros
Flexible working hours (nobody minds if you come in for lunch and then stay late). Relaxed work environment - everybody is friendly and helpful. Bath is a great place to live.
Cons
Very flat management structure - you'll likely be working directly under the CEO. Management is very poor - you'll sometimes have nothing to do for weeks or months at a time. Management also frequently makes short-sighted decisions - favouring short-term payoffs over long-term maintainability. Most of the employees are now full-time fixing short-term issues and bugs that could have been prevented with proper planning. Management refuses to upgrade old systems that are well beyond the end of their product lifecycles. CVS, MySQL 4.0, FreeBSD 4.0 are still in use. The engineers usually work directly on live systems - there is no testing or QA process in place for code before it is deployed.