Well, I'm not quite sure about the title of "Personal Indemnity" to be honest.
There's 'Professional Indemnity' which, if I understand correctly, would cover you in case of a cock-up - say, if you accidentally wiped out data from a customer's hard drive and they lost business because of it and went on to sue you for loss of earnings or whatever. I personally don't (at the moment) have this type of insurance.
Public Liability Insurance, I believe, covers you if you're at a customer's home and stumble over their cat and end up putting your foot through their 42" plasma telly. Also covers you if they come to your house to drop off their computer and they fall down your stairs etc.
Being the sole trader of a fledgling business working out of our tiny spare bedroom, I've had to increase the house (contents) insurance to cover other people's computers that I have in for repair, and I've also had to increase the car insurance and upgrade to business cover to allow transport of computers to/from customer's homes and to allow for travel to work sites if they want me to do the repairs at their place.
All of the above may be correct or incorrect as I'm still finding my way round this maze myself yet, so wait until someone more knowledgeable than I comes along
EDIT: Direct Line "Tradesman Insurance" (weird, I know, but if you search for computer/IT it directs you to Tradesman) is what I've got and it certainly seems to be good value and provide what I need.
