it depends if you are getting it done under local anaesthetic or a daycase general anaesthetic
the wait for the latter is usually a little longer
your gp will know who the local surgeons who do it are and the rough wait - can be up to a few months
a complicating factor outwith of your control is the new hospital consultant contract which affects the way in which surgeons and hospital trusts are paid for this type of work, and if anything is slowing down the number of vasectomies being able to be done
and no it isn't particularly painful
you also need to know it is done with the intention that it will not be able to be reversed at a future date. you will also need to provide semen samples 2 and 3 months post-op to be tested to make sure there are no sperm there before it is 100% safe to go 'bareback'
hope this helps