Hi Easycrank.
I think that you could do much better for your £500 than the 3 quoted in your OP.
If you ignore the 2015 bikes & go for a discounted 2014 model you will get a far better bike for your £££.
I notice that 2 of the bikes you linked have 7 speed & 8 speed drive trains.
A 2014 Cube Peloton with 9 speed Shimano Sora & far better specced can still be had for £499 from
CRC,
Tredz &
Leisure Lakes Bikes for example, a discount of £200 from RRP of £699.
The 2014 Giant Defy 3 for £509.99 linked elsewhere is also a very good bike for the £££ with a mostly 9 Speed Sora set up.
I am almost certain that a little time & patience with Google could find one for a little less maybe.
Both of these bikes are worthy of upgrading as & when parts start to wear out.
Also look at discounted Felt F or Z series bikes from Merlin Cycles or
Wiggle.
What size frame will suit you ? It might help to find a good match.
Steve.