The full table is pulled from a GDS, which I pay for access through ExpertFlyer. If you want to look at your specific itinerary, you can price it on Matrix and pull up the fare rules in a nice format. I don't know the /B405 designator; I'm guessing you have Break from Business fares or this is related to continuous pricing. The latter means that UA may offer a slight discount to the public GDS price if you buy direct or through a modern TA.

Your fare codes indicate some facts about your current price:

• You could go as low as W on the outbound if your flight had W space (or S the day before), which is the kind of thing which is much more like to fluctuate (and can be also found by choosing a different routing, a different time of day except I think ORD-EDI is 1x daily, etc.)
• You're paying an extra $100 on the outbound to fly on a "weekend" (rule '3')
• You aren't staying 14 days, which would save $35 on the inbound fare

GLA has a lower WH287LGT fare which you could use on the return.

For example, this might not be possible for you, but you could go as low as $1,181 (add $90 per direction for non-Basic) if you leave one day earlier and return from GLA. This is about the cheapest you can do while still traveling in your general season, barring significant changes in the fare table (LHR is cheaper both ways, but the problem in Economy is that the savings is less in absolute terms and probably eaten up by the cost of a return train ticket to Scotland).

Some of these are 50-day AP fares and a few (the HH29- high season ones) are 90-day AP fares. So if you don't like the price, you have relatively little to lose waiting until April 25 to see if anything happens, although since there are no change fees you can also book the best thing now and change it if it improves.