Frankly, if you are looking for the best deals I still think it is often worth looking outside the UK. At this price point you are just under the 'utter bargain' modern secondhand Omega price range. There are some nice vintage pieces out there at this price range but the whole thing is very risky without expert knowledge.
So your first option is to save a couple of hundred more, at which point a secondhand quartz Aqua Terra or Seamaster Pro becomes a live possibility
Your second option is to go vintage in which case you will need to learn a fair bit more to get what you want and avoid all the frankens.
Your third option is to go for one of the high end near homage companies: MKII
and Timefactors stand out here (just google them) and get a modern interpretation of a classic from the past. My favourites here are the Speedbird and the Vantage but there are a fair few others.
The quality of the outsides is literally second to none but they are mostly powered by the worthy if mid range ETA 2824.
Your final option is to go for a new mid end Seiko. The vast majority of Seikos offered in the UK are from their cheap end watches, however they have a middle and high end which offers the best bang for buck ratio in the business.
Here dealers like Seiya offer incredible deals on excellent watches
Check out the mechanical Seiko Spirit, it is a credible AT alternative, 90% as good for 10% of the price.
I hope this helps...