Coded landing just means they'll have kept a record of his intentions, on microfilm (they keep the landing card) and their computer system. So they should have it recorded that he only stayed for 14 days, which will definitely help you. As far as I know there's no rule saying you can't visit again for 6 months - just that IOs don't like it if you spend more than 6 months out of the year in the UK.
Yeah, I had a bit of a search around and it basically said that they keep the landing card with the info on there. A couple of the people I spoke to were really helpful and quite sympathetic with my situation, the long distance thing. They said that he will probably get questioned about the previous trip (the reason he was held) and provided everything else is ok, return ticket, enough funds, knows where he's staying this time there should be no problems.
So given that last time, he had no job, no money, didn't know where he was staying, apparently had too much luggage, and looked like a hobo (my words, since his hair is long and curly)...
This time, he has a job (will have a letter from employer), he will have money with him + credit card, won't have too much luggage and I'm making him cut his hair. Shallow I know, but if people are "scruffy" looking, IMO they are more likely to get a hard time.
I'm just really confused by the different answers I'm getting from different people at the Immigration Desk, I called the Terminal 2 one.