Hi,
Are you electrically competent? If not look in Yellow Pages under Vacuum and Electrical Appliance repairs.
Describe the fault to them and ask for an estimate for investigating and replacing the switch. My guesstimate is £20. If you are faced with a £40+ repair consider phoning Vax customer support centre who may offer a reasonable (for a serious fault) ~£60 deal.
If you are competent you need to post the model number.
The switch might have gone due to wear & tear (obviously more likely if its a few years old) but could be due to something else inside. Presumably the plug fuse and cable are OK?
Is there a light on associated with the switch (eg illuminated push-button)? presumably it's not lighting?
Andy3D
February 2011