Having recently researched scopes for my purchase I kept hearing that the Lightbridge and GSO were identical optically, and GSO supplies both their mirrors. If this is so then there is nothing between them. Given that there are local suppliers that hold GSO stock in the size you want, at a very reasonable price, you will save money by picking something that doesn't involve being priced on the new exchange rate and has already landed here (ie shiping cost savings). Andrews Communications prices are very good for what you get and then you can go from there. There are also improvements to the Andrews supplied GSOs in this latest shipment, including much larger and easier to use Altitude adjustment knobs, and the right angle finderscope.
As far as the ability to hold collimation is concerned, replacing the springs with the ones from Bob's Knobs seems to take care that.
As to base construction, I don't see this as a big issue because the base is easily upgraded when required. Is this scope going to sit in an observatory? If so the base may not be an issues for many years. Its not hard to simply use the base components as patterns for building a quality base of marine ply or even strip laminate. You can also buy base kits from the US from places like the Dob Stuff Shop
http://www.dobstuff.com/index.htm
that seem pretty nice. I'd tend go agree with the advice below to buy good optics, and the GSO is very good for most amateur visual observation for it's price, and upgrade other bits as required. Put the money you save towards the observatory and other accessories.
Typical upgrades your going to need would be, a leveling base, setting circles, inclinometre, etc. even if you stay with 'Push to' operation.
Finally, in my limited experience I find that the best investment bang for your $ is to get very good eyepieces which make a big difference in observation quality.
I will be waiting for news on the Australian built ultra -light 20" Dobs.