Have a read of some guides I've written: www.honestjohn.co.uk/insurance/advice/can-you-buy-.../ and www.honestjohn.co.uk/insurance/advice/whats-the-di.../

But why would you want too? The pros and cons are personal to you, not the car. A vehicle that is a Cat D should be for sale for less than one that has not been subject to an insurance claim. They often are not, as the people selling them are generally unscrupulous and look to sell them for the same as one that does not have the history. I would always suggest inspecting every vehicle you purchase, but certainly a previous total loss, especially as you don't know why it was a total loss. If it has not been repaired correctly, it may end up costing you a lot more. So, unless I knew why it was a total loss, who owned it, how it became damaged, how it was repaired and it was at least 20 per cent less than a comparable undamaged vehicle, I wouldn't touch it with a bargepole. If you are going to buy one, make sure you have it inspected by an engineer qualified through the Institute of Automotive Engineer Assessors: www.iaea-online.org/