Why avoid it, I see it as premium work just needs more consultation than other work. The problem is that every area of the country has a different way of dealing with it. The worst area I've worked is Wales, the Cadw can be a real pain but solutions can be found that gets the job done even if it takes months
The real challenge is coming up with solutions and get rounds that meet both the clients needs and the heritage dept's and gets the job done
One tip don't give the client a fixed price for the work and detail exactly what you are doing for the quoted price and variations and abortive work are chargeable as is the time spent in meetings and ommissions deducted, use a duplicate book to track variations in the job ( similar to the architects instructions that are issued on large sites ) get the client to sign it then its a copy for you and one for him as soon as possible price the variation and advise the additional cost or saving to the client, that way you both know where you are up to and arguements will hopefully be avoided