Senor J - I tend to take time off to help the professionals. I have a chat with them and say I am there to help them as much as I can and be there to make decisions so they don't have to assume things which later I don't like.
I always say I like working with them to learn things myself but I don't correct them - just ask questions. With the builder I said in advance I would be there to labour for them and we had a good time doing the work in the end - I have learnt most trades like to take the mick constantly so I set myself up to be the butt of their jokes!!
I've read a lot of threads on here from tradesmen who explain what annoys them about clients and tried hard not to be one of those annoying clients!!
I reckon with this approach I get a really good job done, save money and gain knowledge. Even being nice and helpful to people like cable installers (Virgin) can help - I got a much neater install in my house helping them out.
Saved me a lot of money in the end - at least £2k - and gained a couple of friends and sources of advice!