As a follow up to my previous post, I ordered an upgraded BB. Being a Shimano HollowTech II, the different screw in type BBs are interchangeable. So long as you get the correct thread and width. Mine had the english thread (1.37x24) and the bracket width of 68mm. The bike shop had stock of a Dura-Ace SM-BB9000 in their warehouse, being only a little more than the equivilent Shimano 105 I decided to spring for the upgrade (mine only had a Tiagra, so quite an upgrade indeed).
The BB was pretty easy to fit in the end. Grease the BB threads, put back together, slide in the crank (with a few gentle taps with a plastic mallet drive it home) and a bit of thread locker on the crank arm bolts.
I also gave everything a really good clean whilst it was apart. The chain rings were quite filthy and there a few places that are difficult to reach when it's all together.
The dropouts were something else I addressed. When I first got the bike it came with Skewers that were cheap and didn't have a lot of clamping force. Initially the replacements I got helped, but the damage was done and it indented the dropout in the wrong position. No matter how much force I used, eventually the wheel would find it's way into that incorrect position. Lately it's been happening nearly every day, which was driving me mental.
So it gave me a chance to use my new found favourite product, JB Weld (2 part epoxy steel resin). I filled in the incorrect position so I could reset it and create a new one. So far it appears to be working quite well. Though I need a new skewer as I cracked it with all the force I had used to try and stop the wheel from moving.