Welcome to the UK philosophy (perhaps that should more correctly be the GL philosophy!). If you need any advise just post on here or the VOD, there's always people willing to help.
With regard to moving the venturi, I would certainly agree with your thinking ... I did the same with my processor when I first built it. It seemed wrong for it to be located lower that the oil level in the processor. The higher position usual means the it has to be positioned horizontally which has, in the past, not been considered the ideal orientation. That said there are many who have fully operational venturies working horizontally, myself included. In fact I've had several designs of venturi all perform well when horizontal. Only one failed to establish suction and that was cured after a little research of various manufacturers websites and some experimentation. The solution was to install a jet splitter, shown at the bottom of the venturi page on the wiki.
Ironically I have a feeling that venturies which are accurately made are more prone to "jetting" through the discharge cone. Most of mine have the throat drilled to size on a lathe and hence are likely to suffer the problem. With your venturi, it may pay you to first try it as a "welded finish" and see how it performs, them drill the throat if necessary.
I've always thought that working with steel pipe must be a right pain in the backside, you have my sympathy, but your solution looks to be an excellent one, nice welding as Tony says.
Good luck with the build, as you say you'll have to bite the bullet at some point. Don't try and attain perfection ... if you are anything like most serious home brewers over here, you'll be modifying it within a couple of months as new ideas and processes come to light!
