Second those comments about the schwalbe- they are the only feasible option for 597 rims these days.
I use them on my daily commuter - which is a 1950s Raleigh Lenton- and it usually sees 2,500 miles annually (pre Covid that is...). I get through one rear tyre a year and the fronts tend to last several years.
Reasonable tyres to be honest. Not the most puncture resistant but I’d hazard a guess I get no more than 8 every 2,500 miles which isn’t bad considering the state of London’s roads.
As for converting to 700c, my aunt’s 1950s Carlton has 700cs and the drawback is that the max width tyre she can use with mudguards is 28mm, which some might find too narrow but I guess it all depends on the look and riding experience you’re going for. Other frames may well give more clearance anyway so it’s always worth double checking first.