Has anyone heard of or had their car chipped, or mapped as it's sometimes called ? I'm seriously thinking of getting it done. It involves having the cars computer re-programmed to give you better performance and better fuel economy.

yes my T5 is done......its great :) but get it done by a reputable firm as like most things there are cowboys out there :(

that sounds interesting does it cost alot ?
ps when I first saw this is was thinking along the lines of chipping our dogs and wondered how that worked lol

How does it work? Would it invalidate any warranty?

We bought one when we got our car as it really guzzeled up the diesel but tbh the fuel economy wasn't much improved nor was performance (for the price of the chip, I mean).  We have ours up in the loft now as we took it back out.  Like someone said, you get what you pay for but ours wasn't a cheap  chip.

we improved BHP from 130 to 175 and fuel economy by 7-9mpg depending on the journey type. it cost £300 to have the enginne remap and doesnt effect my insurance.

Now a days it's the on board computer that is " mapped" rather than a chip which is put into the car, I've had a look about and Auto Trader suggests that you should wait until your cars warranty has run out before you do it as it will affect it. The site I looked at which has agents all over Europe quoted £359 for my diesel Honda CRV, but it says I'd have made my money back after 12,000 miles, it also gives you a 7 day money back guarantee if your not happy and a life time warranty against corrosion of the mapping, it will also keep your cars original settings on file in case you want it reversed at any time. Some cars seem to benefit more than others, turbo diesels work well as do VW's and Audi's...supposedly.
I'm going to look into it a bit further before I go ahead but it looks quite promising.

They give you an average BHP reading which is always on the high side and the only true way of finding out your BHP at the wheels is a rolling road tune. You will have to inform your insurance and its not standard and depending on insurance company they may add to your policy.
Some will see a small increase in speed and fuel saving but how you drive has much more to do with saving on fuel than a map or chip.
Yes your warranty will be void if you start messing with it but some manufacturers do offer the service but it tends to be the bigger sport jobs and its worth talking to your main dealer first.