Hi Calvin,
I'm nearing the end of my first role within the public sector and there are notable differences between public/private sector procurement. The biggest difference is OJEU and getting your head around the end to end process which takes ages and is complex. The other key difference compared to buying for a private sector organisation is that from my experience there are few opportunities to actually negotiate with suppliers, there is certainly no scope to attain the best possible commercial deal.
Interim buying roles within the public sector tend to pay more though which counters some of the frustration
PM me if you need any more help or info.
Ferdy