Robust bike for Racing AND Touring?

Sportifs aren't racing.

A cross bike sounds like a good option but I think you may struggle to get under £500?

I got an entry-level Kona Jake (Tiagra) that's served me well for four years.
I do most of the household shopping on it and seldom and very reluctantly go off road or cycle track: logged 4,500 km last year. 

I've had two crashes in which the bike proved its mettle.

In one, I was doing more than 20 kph and ran into a concrete kerb stone concealed by grass.

Bike was undamaged.

In another I was doing around 30 kph when I hit  a roadside barrier square on (long story). I was flipped over the barrier and ended up sprawled on my back with head pointing towards the bike. Naturally, I hadn't unclipped, and I suppose that had something to do with spraining my ankle and having the rear wheel buckled . I managed to ride the remaining 12 km home.

When I finally inspected the bike, I noticed only a dent on one side of the CrMo fork. No twisting or anything, just a dent. Not fatal in anyway. The rear wheel couldn't be trued, it had to be replaced. If all cyclocross bikes are built that way, then they are robust enough.

Two things I could live without.

One is that because the wheelbase is rather short on CX bikes, even without mudguards, you need to get into the habit of feet at six o'clock when using the handlebars for steering.  I'm still working on my technique for climbing zigzag wheelchair access 20 vertical metres up a back way into a local park. It's hard to go around tight corners when the front wheel hits your foot.
The short wheel base also means, to avoid heel strike,  you should carefully select your rear rack and get panniers that can be set back.
The bike may be a bit twitchy, but as I don't have experience of much else, I haven't noticed (even after 350 km on a three-day tour). 

The other thing is the rims. Cheaper bikes come with affordable wheels. The rule of thumb seems to be max. tyre size = rim width + 50%. If the rims are 16 mm wide, then 25 mm tyres are the theoretical max. Sure, you can squeeze 28s on there or, as I did, huge Schwalbe Marathons (I think they were 37s). But it's not ideal.

I really love my Jake. OTOH I do have a hankering for a BMC GF01 or a Synapse or similar 8 kg bike. I know several people in a local group who have Enduraces and go on rough roads and gravel. The bikes stand up well: tyres are consumables. 

I agree with what CXR94Di2 says. A cyclocross should suit your needs. The forks on a road bike won't have the clearance for larger tyres.

I think after a bit of research into I'd be looking on Ebay - For £500 you'd probably find a pretty decent quality cyclocross within your price range.

I would get a cyclocross frame for racing, then add larger tyres for endurance/cobble riding.  Make sure there is enough fork stem to adjust height and reach of handlebars, or fit a BBB stem riser.  Many decent cyclocross frames come woth eyelets for mudguards.  No need for two road bikes other than having them

would your Canyon 'endurace' not be designed for longer journeys? Can't imagine it would break at the first hint of a cobble!

If not, then I think you may need to look at the second hand market to get something that meets all your requirements in budget..