It is entirely possible to pick up a really nice quality, albeit dated, road bike for £100 or less. I got a lovely late 80's raleigh with 105 kit (old - downtube shifters etc.) on a 531 frame for £40. You just have to take a bit of time looking and you need to know what you're looking for/at (or get advice on here!).
The advantage is that, if you find something with good quality kit on then chances are it will last loads longer (the equipment etc. in terms of reliability) and be just as quick as an entry level bike you could buy new.
The advantage is that, if you find something with good quality kit on then chances are it will last loads longer (the equipment etc. in terms of reliability) and be just as quick as an entry level bike you could buy new.