ok, what I suspected, just that I was thinking changing at Peterborough may have been cheaper than going via London but it turns out I might have a meeting in London for a couple of hours at least 1 way so probs won't bother wasting my time playing around with fares
cheers
It's the same price, so I would get the Potters Bar ticket, and you can go either way on each leg.
If you purchase an Off Peak or Super Off Peak fare, and travel via London, the restrictions apply to the 'InterCity' part of the journey and not the 'connecting' part of the journey, e.g. you can take any train from Potters Bar to King's Cross, but you are restricted based on the time of the trains departing King's Cross). If you have any questions about this, please ask.
A useful website to plan the journey is
www.fastjp.com (you can specify maximum 1 change if that is of benefit to you, and if you want to see itineraries that involve speedy changes between platforms at KGX you can do this by choosing Go via: type KGX, tick must change here, and type a negative value of e.g. -10)