I would say £300 gets you a usable bike, but expect to have to repair / upgrade fairly quickly. I would go second hand, or stretch to £500 and try and get a good deal.
My friend bought a £300/400 Halfords road bike recently as he had signed up for an event. He’s really enjoyed it and it has got him into cycling. I serviced it for him recently and I would have some doubts over the durability. It also wasn’t very well set up, with bizarre cable routing that really hindered the brakes and a few other niggles. The things I thought were good about it:
– Gets you out for a low cost
– Reasonable (usable) weight
– Set up like a proper road bike
Downs:
– Double chainset. What on earth the majority of people buying a £300 road bike want with a double chainset is beyond me.
– Some strange low rent shimano parts. You will need a spanner and socket set to assemble, put it that way.
– Poor quality tyres
– Wheels significantly out of true after 6 weeks use