Thanks for the nice comments.
I also used Tec7 black bond to seal all the outside edges as future proofing against ingress of water.
It's more expensive than ordinary silicone.... maybe €13 per tube, but it's easy to spread with a latex glove and some white spirits to help glide along. I used 4 tubes in total to cover all the edges from front to rear. No issues with ingress since.
Mind you, whomever installed the solar panel used tex-screws to secure it in place.... and therein lay the culprit for water ingress.
A botched after though roof vent didn't help matters either somewhere along the years
.
No matter, we're back in action, sealed, dry, and a far snugger camper then original. The 30mm floor insulation board (foil both sides) is a serious heat retainer. Can wait to head down to Doolin next weekend to face the cauld Atlantic to test it.
It's a 5 Berth, coach build, sitting on a Ducato chassis, the old 2.8d...87 Horses engine!
Tullamore to Wexford and home...1/2 a tank... so that's fair miles to the gallon considering.