If you were to tell someone "I just bought a 1986 Jaguar XJ6", or "I just bought a 1967 MGB", what would they say?  Usually they tell you that they have electrical problems, leak oil, they are unreliable etc.....Well, even new cars may have reliability problems.  We must keep in mind that these cars are anywhere from 20-60 years old!  Most of the problems you will encounter are old car problems.  Not to mention that many people let them sit for long periods of time, wich is one of the worst things you could do.  Maintenance is THE most important thing, especially with more complex cars!  I have driven cars that were almost brand new, that have had rod knocks and other major problems.  Old cars leak oil because the seals and gaskets age, thus causing leaks.  Wiring ages and builds up resistance, wich generates heat .  It is true that when British Leyland took over, many had quality problems.  My parents bought a Triumph Spitfire in 1980, the last year made.  This was in the midst of the labor problems.  It had runs in the paint, used oil, no grease in the rear wheel bearings, but all fixed under warranty.  Once an old car is "sorted out", it will be reliable.  At this stage of their lifes, the problems you will find are usually due to the following: 

1)Age

2)Owner neglect

3)general wear and tear

4)try not to worry about the "mileage" on the car!  Mileage is good for service intervals(and car dealers.....), but again, MAINTENANCE is the key!  A "low miles" or "1 owner" car does not make the car a good buy.

If you like working on cars like I do, you could always buy one that needs a little-alot of work.  If not, many mechanics will work on them.  Also keep in mind that classic cars are not like new cars.  They feel, stop, and respond differently than a "modern" car.  If you think a classic British car is for you, I would suggest the following before buying:

Make sure you know wich one you want!:)

1)Buy the best you can afford(A common, but very good suggestion!)

2)RUST-It usually takes less money to renovate a car with bad mechanicals, than one that has structural rust.  Check the rockers(under the doors), floor pans, and the lower parts of the wings(fenders).

3)Try not to get TOO excited upon a potential purchase!  I made this mistake when I traded my Jaguar for my MGB.  Many of these cars are not rare, so try to take your time. 

4)Body-You can use a magnet to check for areas with too much body filler(like mine!).  Keep in mind that unless you do the work yourself, body-work can be expensive!  If it only needs paint, preparing the surface and masking it youself will save alot of money.

5)Mechanical-Check for unusual noises or vibrations.  A certain amount of noise is normal.  A Jaguar XJ6, or XKE with  the 4.2 liter XK inline six cylinder, for example can work it's valve guides out out of the head.  If left this way, they will eventually come in contact with the cam!   The exhaust side of the head on Jaguars with emissions equipment build up more heat, thus causing the guides to work loose.  A "stake-down" kit will solve this problem.  However, on a engine such as a B-series engine in an MGB, a "clackity clack" sound from the push rods hitting the rocker arms is normal.  Any kind of KNOCKING sound is NOT normal!  A knocking sound would certainly mean an engine rebuild, at least the bottom-end of the engine.  Check for smoke on acceleration/de-acceleration.  White is coolant in the oil(a "sweet" smell from the exhaust, could be a bad head gasket, or a cracked cylinder head.  Blue smoke on start up would be the valve guide seals, on hard acceleration it's the piston rings.  Black smoke is unburned petrol(gas, sorry!).  The brake pedal should feel solid all of the time.  The clutch should not slip, and if it engages close to the end of the pedal stroke, it is probably a worn friction disc.  The car should, of course, drive and brake straight.

I don't want to make this too long, but I wanted to cover most of the major things.  These cars are amayzing!  If you like a solid ride, an "old" feel, and GREAT character, you will love these cars!