peanut said:
All I am saying is that the op should make sure that the componentry of a 30 year old bike IS up to scratch
Ah, if only that *were* all you said...
That aside, my last word, FWIW, is that you can get a damn fine bike off
ebay for £100, if you choose carefully, do your homework, and are prepared to be patient. If you have £200 to spend, the world of fine '80s bikes is your lobster.
At that kind of level and upwards, any bike you choose is likely to have started out with quality componentry - 600/105 or thereabouts - and been looked after by the kind of enthusiast who had several hundreds of pounds to spend on a serious bike back when several hundreds of pounds would buy you most of Lincolnshire.
Good componentry lasts forever. Well, not forever, but decent 30 year old stuff that's received competent maintenance will be fine. Swap an email or three with the seller, to gauge what kind of person you're dealing with, and you should be ok.
It is of course possible to come a cropper. As it is buying a new bike. But the answer to your original question - Are old road bikes any good? - is some are, some aren't. But some that are are very good indeed. And many that are are way way better than anything you'll get new for that kind of money.