If you are thinking of doing a self build then my advice is to join a proper GOOD & ACTIVE self building forum group, there are a few of them around and the help, support and help they can give, can be totally invaluable.
Our free to join sister group Motorhome Builder is very sadly, nowhere near as active as many of us would like it to be, but never the less those members on there have an enormous amount of help and advice ready to be freely given.