Buying a car that has been in a crash and needs repair is one way of getting a decent car for less money - but only if you have the skills to repair it ..... and properly.
Insurance companies sell by auction some categories of write-off to dealers who may then legally sell them on to Joe Public. Only Category C or D should be sold on. D's are usually very lightly damaged, typically a forced door lock and damaged ignition barrel. All Category C vehicles will need a VIC check before DVLA will re-release the impounded logbook. The Vehicle Identity Check is "... used to confirm that a vehicle being returned to the road has been repaired following accident damage and has not been stolen." Current charge for a VIC is £38.
So - if an ad on eBay says Cat C and " ...may need a VIC check" (or doesn't mention it at all!), the seller is being economical with the truth. It MUST have a VIC check to go back on the road.
Be very wary of any seller who states "light damage". There is no legal definition of light damage so may well be seriously damaged.
Some auction firms and some 'private' sellers employ one very underhand practice. They partially 'pull out' the damage with hydraulic equipment. The aim is simple, to make the vehicle APPEAR less damaged and therefore get a higher price. If you go to an auction, strike up a conversation with a regular buyer and get round to the subject of 'pulled' cars. If that particular firm does it - then my reaction would be to NEVER risk purchasing from them. On a lesser scale you may well see evidence of a bonnet or wing that has been crudely thumped back into rough shape. Again, take it as a sign of someone probably trying to pull the wool over your eyes as to the true extent of damage. One or two of the big firms do it.
Never buy a crash damaged car unless you can physically inspect it.
It may have been driven off the road and have sustained major damage underneath but that is invisible in pictures.
You will see vehicles listed as "unrecorded". This means that they have not been listed on DVLA's database as damaged - but may be very seriously damaged in fact. Sadly the system for recording vehicles with crash damage is VERY flawed. Many badly damaged cars are not getting on to the list which was intended to safeguard the public. So an HPI or similar check when buying any used car is not 100% safe by any standards.
Large companies 'self-insure' their cars and so when one of their damaged cars gets out onto the open market there is no record for HPI to discover.
If you keep tabs on eBay you will see vehicles with very serious damage - but strangely listed as Cat C, when in fact they should have been classed as Category B (which is trade-only, break for spares and not to be repaired).
You will also find private sellers with crash-damaged cars that have not been insurance assessed because the seller only has Third-party insurance or is a young driver trying to build up a no-claims bonus and so choose to write the car off themselves. That is OK - but you need to be wary when they say "easily repairable" as it may well NOT have been looked at by anyone with professional skills.
Buying a car with mechanical trouble or as an MOT failure is again only for those with above-average mechanical skills. eBay is full of Vauxhalls, Rovers and Fiats with blown head gaskets, plus all types of cars with snapped cam-belts, defective brakes, 'excess corrosion' etc, etc.
It is a minefield - so, again - you should ideally inspect the vehicle . If you cannot inspect it, keep your bids low so that a total scrapper doesn't wipe you out. And with Grasping Gordon supertaxing fuel and motoring in his Milk-the-Motorist plan, work out carefully how much you'll spend on trailer hire and fuel before deciding your maximum bid.
Finally, think laterally. They may be selling the Corsa "because the head gasket has gone" but it may well also be suffering from typical Corsa terminal rust in the front floorpan area near the suspension mounts .....