The offer you were given seems a bit low to me, but maybe the prices have lowered a bit, in the last 6 months or maybe retrospective to the deal you are doing.
In March I traded my manual 997.2 C4 in a nice spec & manual so quite rare on 45K miles spec for £37000 main dealer Porsche,
They have just sold it to someone for circa£42k with OPC warranty which I think is fair enough given they will detail it beforehand & give the cherished warranty.
They didn't have to do much as it had had everything done by me beforehand, lots of maintenance coolant hoses, steering rack, belts, filters plugs, brake fluid, service, etc etc but still fair I think based on the deal I got on my trade / next one.
So I'm thinking £34k for a 4S which is a potentially better variant (subject to condition) is a really good price for them a buyer :?:
Depends what you want or have in your car I suppose.