A 1972 MGB is actually one of the better years of the marque, as are most of them before the terrible "rubber bumper" smogged cars of 1974 onwards. You WILL become a mechanic if you own one. Parts are still available from places like Moss in Santa Barbara
www.mossmotors.com and Victoria British in Saint Louis
www.victoriabritish.com .
Mazda has sold over 700,000 Miatas for the reason that they are all the fun of the old British sportscars with the ease of ownership of a Honda Civic. I'm on my second one now. The only reason I sold off my 1992 Miata is that the 2004 was a much better platform to turbocharge.
A Miata with 150,000 miles on it will be a MUCH more reliable car than a carefully restored MGB. Try a 1.6l car from 1992-93 or an early 1.8l car from 1994-95. These should be available for about $3-4K for a low miles decent car. See
http://forum.miata.net/vb/ .
I've previously owned a 1954 Austin-Healey 100-4, a 1959 AH Bugeye Sprite, and other British cars so I know from where I speak.