There are many factors involved in live rates, so before you start thinking about rates you need to work out what sort of event it is and what the client expects. Remember, anything above the pub circuit is considered a professional outfit and as such, the fee is likely part of the musicians living. Here are some rough Rates:
Corporate Events (£500 - the sky is the limit with these things)
Function/Private Party/Wedding (£500 - £1600)
Pub Gigs (£150 - £400)
Originals Gig (ticket cuts if you are lucky)
Number of band members: £1200 looks nice, but split 10 ways, after expenses, isn’t much. Same fee for a 3 piece outfit and its a nice fee.
Playing times:
Corporate: Anything goes. These events generally have BIG budgets so they expect a lot from you. Expect early set ups, long sets and specific
Function/Private Party/Wedding: Anything from 2×45 minutes to 8-12pm with a couple 20 minute breaks.
Pub Gigs: Anything from 2×45 minutes to 2×1 hour sets.
Originals: As long as you can get normally :D
Distance Traveled: At the moment the Musicians Union are stating 15p per mile after the first 30 miles. This goes to and from the venue and is on a per musician basis. Again, £100 for a gig sounds nice, but add 5 hours travel time each way and it stops adding up as well.
For detailed advice contact the Musicians Union.