sluggish starting

[WillNZ]

You should go around the engine bay and do the same for all ground connections for the loom, especially look for the one hidden by the fuse box. Also, have a look under the RHS front carpet and make sure the large connectors under there are not wet/corroded. When they do get wet/corroded, they cause all sorts of issues with starting/running/electrics... never had a 406 where I didnt find water/damp under the carpet there.

[frog]

especially look for the one hidden by the fuse box.

That one. Peugeot calls this fuse box the "BSM box". There is a vital, essential, very important ground connector under it.
It is a bit of a fiddle to get the box out of the way to access the ring terminal connector under it.

If i recall correctly, this ground connector is also for the "BSI box", which can get very stressed if it is disconnected from the battery in an uncontrolled way. If you want to take out this connector in order to clean it, make sure to apply the "3-minute rule" (http://www.petercoopercarrepairs.co.uk/ ... cedure.htm, or just google for "3 minute rule bsi").