After growing in a south facing grenhouse fot the past 6 years, I now find that the only place I could situate the greenhouse is north facing.
I think it will get warm enough as it does get some sun.
Will the plants stretch too much or will they be ok.
Any thoughts on this matter would be appreciated

You should be alright, most greenhouses use some kind of shading in the summer to prevent overheating and scorching. On a cloudy day (and in winter) the best quality light actually comes from directly above