So I had an opportunity too good to pass up. Long story short, some unexpected budget, some excellent generosity of Amazon in allowing me to return my 630 after 2 months and I am the new owner of the Fenix 3 (with chest strap).
I didn't actually purchase it from Amazon, I bought it from millets.co.uk/equipment/215...
For £285 it was unbeatable - Amazon's equivalent is around £350.
As a watch it is much heaver (twice the weight?) of the FR23x/630, but it is a thing of beauty. It feels like a good solid lump of engineering where the 23x/630s felt a bit plasticky.
It also has a really useful feature which is you can upload navigational routes (Garmin calls them courses) and the watch will navigate for you.
It looks, acts and feels like a top of the range watch. Love it.
As ever with these things, I am probably only using 10% of its capabilities, but everything it does it does brilliantly well. Even down to assigning 'hot keys' so you can decide what should happen when you press and hold one of the buttons.
So yeah, if you happen to have a big chunk of change hanging around and want a watch that will do more than you could ever ask then millets is ridiculously cheap at the moment. Next day delivery was only £5 and they use DPD which means you can watch the delivery van on a map in real-time. I keep expecting them to issue a price-correction - the HR bundle is cheaper than other retailers are selling the just the watch for.
I also recognise that I am incredibly fortunate to be able to have a watch like this and am very thankful - it rocks :-).