Hi Suzy
Just chiming in with another welcome.
My own mum is 88, formally diagnosed about 18 months ago, so I have some idea of how you must be feeling. It's a worrying, anxious time. Once you've made sure he's got all the support available locally, you can really only take things a day at a time. Apart from the sort of daycare available through social services, Age Concern also do quite a lot of daycare groups, including those tailored for dementia sufferers. May be worth enquiring about.
Phone often (there may come a time when the use of the phone is beyond him), say all the things we Brits are usually so reserved about expressing out loud, take photos on good days, send little cards & notes if he can still read (my mum's eyesight is going, so she can't - not directly related to dementia, wet macular degeneration).
And don't forget to come back here often. The accumulated knowledge & experience found here far exceeds that of the medics. Talking Point is a sanity saver.
Best wishes