Nice 401 Darren.
You have a twin spark suppressor type (Flush strobe, non serrated) which as you said is an earlier type and more desirable than later type 401's. The strobe assembly is more complex and the cosmetic finishes (Fascia plate etc) superior to later versions.

In terms of basic servicing:
Clean the inner running face of the platter Using isopropyl and a lint free cloth
Clean the pulley - Using isopropyl and a lint free cloth
Clean the running face of the idler wheel Using purified water and a lint free cloth
Check for play in the idler housing bearings - place fingers on the periphery of the idler in the 12 and 6 o'clock position and rock alternately. Then try the 9 and 3 o'clock positions - any movement?
Check for play in the spindle - Place fingers on the periphery of the platter (Whilst in situ on the spindle) in the 12 and 6 o'clock position and rock alternately. Then try the 9 and 3 o'clock positions - any movement?
On the underside observe the idler housing arrangement there are three rubber grommets attaching the assembly to the chassis - are they dry / deteriorated?
Remove the spindle housing from the chassis, remove the base plate of the spindle housing and remove the thrust bearing and spindle. clean the bearing, spindle and the inside of the housing with isopropyl (A small bottle brush is handy) prior to re lubrication of the felt washer (Sits on top of the housing at the base of the spindle and feeds the top bush (Lubricate liberally), the small screw close to the base of the spindle (visible on top of the housing) gives access to the oiling chamber for the bottom bush - Oil liberally)
Remove the idler wheel from the idler housing (Two screws) clean the pins of the idler wheel and lubricate the top and bottom bushes
Check none of the springs (Visible on the underside of the unit) are visibly stretched out
You may note a loud bang noise emanating from your speakers when switching the unit on or off...This will be the spark suppressors which will likely need replacing if not now soon.
You may note I have not mentioned the motor which ideally should be stripped down and rebuilt this is due to the felt oil reservoir lubricating washers which are likely to be either dry or 'varnished' from age old oil the same is true of the bearings which are sintered bronze (Porous, they get clogged and can not fully retain lubricant (These can be heated to leech out the oil prior to heated re lubrication) . To gain access the riveted top and bottom plates need to be removed, to reveal the the bearings and felts. This process is fairly straightforward and well documented however options on re affixing the plates vary from nut and screws to re riveting.
As has been previously mentioned a greasing of the linkages at all contacts and joints is a good idea.

Tips:
Use a light flexible power cable as the motor is suspended and a stiff or heavy lead may push or pull on the motor which will cause noise.
Speed can be adjusted by moving the magnet closer (To slow down) or higher to speed up the unit. This adjustment can be made via the small screw visible south east of the idler housing cut out on top of the chassis (Visible with the platter removed)

For checks on what constitutes a buggered 401 see: