Managed to squeeze in a little progress this week...
Some of the nuts on the frame were already working loose (as of last weekend), so after skimming the forums for suggestions - I ordered 10ml of Loctite 243 ThreadLocker. As of yesterday, I've now put a dab of loctite under each nut on each vertex, plus those around the Z-motor mounts. This also gave me the chance to fine tune the distances between each vertex.
The smooth rods were fairly grubby and there was far more friction on the X/Y axes than I'd like. So.... a few minutes of judicious scrubbing with some wet wipes cleaned the rods, followed by a light application of lithium grease (Castrol LM Grease) has made a big improvement.
After my initial assembly, the Y-axis belt met the bottom plate at quite an angle - especially when at a min/max extreme. After a bit of research, this seems to be because the design is intended for a 10mm thick bottom plate - whereas mine is only 6mm. The solution was a couple of ply offcuts to raise the height of the belt mounting point.
The standard Prusa places a nut between the Y motor bracket and the belt pulley - this seems unnecessary and causes additional strain/flex on both the motor shaft and the Y motor bracket. Removing this nut didn't take long and has not only reduced the moment on the motor/bracket, but has also given enough clearance to properly centre the Y-belt against the bottom plate.
RAMPS in the house
The RAMPS kit I ordered from xyz printers arrived yesterday - will get started on soldering that this evening...
A Mega issue
The arrival of the RAMPS kit prompted me to check that it would fit properly on the Seeeduino Mega, only to realise that I've been a complete idiot and somehow missed the fact that the Seeeduino Mega is not pin compatible with the Arduino Mega! and therefore not compatible with the RAMPS shield! :(
I did consider creating a frankenstein mating of Seeeduino and RAMPS, but then thought better of it and ordered an Arduino Mega 2560 off eBay for ~£24. It dispatched this morning, so hopefully will be here on Monday.
I'll keep hold of the Seeeduino Mega for now, as I have an upcoming project planned that will make use of the hardware...