A update for any one reading this in the future. its a summary from all the good info from above.
I bought:
Claris flarbar integrated shifters and brakes from the Ribble link for £20.
2 inner brake cables as the flat bar ones have different shaped ends. £4
A pack of cable end caps. £1
Tools
The usual hex keys / screw drivers etc..
Cable cutter for the brake and gear cable inners.
Took me 2.5 hours all up but probably a hour if I was to do it again. Not that hard a job – just a tiny bit fiddly with the internal cable routing and aero brakes mounted behind the fork and bb. The Claris flatbar brake leavers pulls the road brakes correctly.
I reused all the cable outers without shortening them – looks a bit messy.
The stock 70mm stem was swapped for 100mm. Same 7deg rise. Feels ok. I’ve got a 80mm and a 120mm I can play with later.
Handling wise around town and such I love it compared to drops. Yet to go any true distance but i expect I’ll be a spinnaker if there is a head wind.
I’m guessing drops will never be for me.
Thanks again for all the good info i got from here.