Depends...
Easy "quick wins" would be the charger harness and the rear light SS bolt conversion. Purely because for a few £ saves big bills later.. harness (wire in the trickle charger for the batter to make it easy to use - hence you use it regularly) and saves you purchasing £100+ batteries on a regular basis.
The rear light bolt swap (mild steel lense bolts to SS versions) saves you having to pay 1-2 hrs labour to change a bulb!!
Oh.. I would put this third...
Re-secure the rubber beading around the cowel.. these are notorious for coming loose... Morgan used a less than fantastic glue to attach these (some are only taped on!!) and combined with stretching them round a curve (inner edge of the cowel) cases the rubber to attempt to pull itself off the cowel due to it's own internal tension... net result... rubber piping that eventually flapps out over the wheel arch and scuffs the paint.
Once this is sorted...
If you have the "click" characteristic on start sometimes then the engine tray mod along with the starter mod. (S2's don't have the tray so this is not so much of an issue).
The Bonnet Catch depends on the angle of the part attached to the wing.. some are ok others do not hook properly.. not too much of an issue generally until you push on and then bonnet pops up.
The roof mod depends on what version of the S1 version-1 roof only... an interim fix from the factory was to sew on a channel for the window to come up into..
One characteristic you'll find is purely down to the "handed-ness" of the fabric passed through the sewing machine... the beading used to finish the channel on one side (usually the drivers) lippes in wards at the front edge where the window meets the top of the "A" pillar thereby protecting from rain ingress by altering the airflow at that point.
On the passengers side however this lip pulles the fabric outwards causing rain to be effectively scopped in to the small gap between the side window and the "A" pillar thereby allowing ingress of water. By inserting a small piece of wire into the bead it allows you to shape the lip inwards to re-direct the airflow as the drivers side. Without affecting the Roll-ability of the roof when lowering it.
Finally ECU re-map.... when combined with the ITG induction swap should get the S1 up from about 289bhp to about 320ish.
Of all the recommendations I would put the ones that save bills later at the top.. so:
1) Battery charger system - saves batteries
2) S1 starter fuse upgrade 30A fix - saves you from calling the AA
3) Check Bonnet Catch - saves you from heart-attack
4) Rear light bolts - saves you from labour to remove inner boot lining
5) Roof mod (depends on model) - saves SWMBO from getting wet thereby self-preservation
