Remove wiper arms. At the end of each wiper arm there is a black plastic plug that covers the bolt. Helpfully each one has a little lug on the side. Use a thin flat blade screwdriver to apply very light leverage, and off they come.
That reveals the 14mm nut holding the wiper arm in place. Remove them from each wiper arm and pop them to one side. I found the best way to remove the wiper arm was to flex the arm slightly on it's springed hinge - that "straightens" the arm on the "spline" that it's fixed on. Then it just lifts off, hopefully with no bother, and minimal 'jiggling'. Put them to one side after a quick spray and wipe with WD-40.
The next step is to remove the plastic scuttle panel. The panel comprises two halves - left and right, overlapping in the centre. On mine there were seven screws holding this in place:
3 x Torx screws - one in the centre of each of the left and right panels, and another in the dead centre, where they join.
At the top of each side of the scuttle, at the leading edge that mates with the windscreen, there is a black plastic circular plug. It is just a push fit. Prise them out gently with a thin screwdriver. The plug is attached by a little plastic t-bar. Gentle pressure will free it, so be careful not to lose it. Under the plug, on each side, you will find a small, rusty phillips screw. Mine came out easily and I bathed them in WD-40. I've heard of people having to drill the suckers out.
OK - at this stage the scuttle feels "looser" but is not going anywhere fast. If you look below the scuttle and to the side (i.e. towards each wing) you'll see another screw. This is mounted horizontally
(all the others were vertical). They come out ok but you need to be very careful not to allow them to fall down into any of the nearby nooks and crannies.
Some folk have suggested that you need to pull the rubber seal off that runs across the scuttle at the back of the bonnet. I didn't, it came with the panel - no problem. There are some plastic clips on the rear edge - just ease them out. I took the opportunity to wash the scuttle inside and out, and clean the base of the windscreen where the seal was. It gets very clarty. The washer jet pipes are attached to the underside of the scuttle, so go steady.
I did a general tidy up while I had access - removed a shed load of leaves and compost. I noted that there was no rust at all and cleaned it all out and sprayed with WD-40.
Then the easy bit. The wiper motor and linkage is held by 3 bolts. Remove them and unplug the electrics. Jiggle the unit out. Fit new unit as reverse operation.
Replace the scuttle and give every nut, bolt and screw a slather of grease. Once again, be careful not to drop and lose the horixontally mounted screws. I blobbed some vaseline on them and that gave enough "stick" to get them in position.
Pop the wiper arms back on, and replace all the plastic plugs.
Give it a go!