Yeah, in my personal experience Dr Richard North is good. He is part of a longtime Eurosceptic intellectual ciircle. Richard is polite and engaging (unlike his son who is intelligent but mad as a box of frogs). He was the lead author on the only detailed, thought through Brexit plan I have ever seen. Several times post referendum I had questions on it and he was quick to answer me, point to other reading or source documents and explain his reasoning. He is a long time eurosceptic from deeply held legitimate concerns about the long term effect the EU might have on the power of the British people to effect change on their own lives at a local level and the ratchet effect of bad ECJ rulings.
What he does acknowledge is the value of a lot of the Trade structure the EU has devised. It is difficult not to, the more you understand about it the more impressed you become. Unfortunately not many Brexiters have bothered to do this. If they had then even if they still wanted to leave they would have been saying, hold on, this is going to be bloody complicated to extricate ourselves from without causing a lot of damage, Brexit is in fact not a thing but a process, so let's make a detailed plan before we start a clock ticking.
However, I'm not sure North is going to be of particular insight into the negotiation process, compared to some of the other people I've linked to who have been advising and assisting Parliamentary groups and, as in the case of Dmitry Grozoubinski, has actually negotiated Trade Deals both with the EU and for the EU in the past, or Peter Unguaphorn who was 14 years at the WTO Secretariat in a very senior capacity.