all screens are measured diagonnally. One difference between CRTs and TFT/LCD is that the nominal CRT measurement is typically about 1" less than the viewable size (as part of the CRT is hidden in the casing), whereas TFT/LCD nominal = viewable. So a 15" CRT is roughly equal to a 14" TFT/LCD.
If you are not going to be too critical you'll probbaly find that most are up to the job. As it happens, I saw this 19" SONY on ebuyer today at £141. click here.
Also, have a look at the customer reviews for various screens on ebuyer, dabs etc.