Nice going deano, a shed fire is something we all dred , even small ones like yours, makes ya really think what could've happen. Glad you controlled it without panicking..
A friend of mine had his shed melt with 2x mk1 Escort coupes cooking away with nothing he could do but watch and cry. Culprit was a Makita charger so when your done, flick the switch off regardless if it's not charged.
All of my chemical tins like paint, thinners, resin etc etc are kept in a metal cabinet in another closed off part of the shed.
Those side plates look fine from here 👍, you should be happy. As with the heater bubble panel, it's up to you. If you glue it on, use some gasket maker type of silicone, good bonding but easily peeled off when needed. If you weld it on, remember to use sika joint sealer on the inside under the dash to stop any pin holes causing leaks/rust. Also drip paint from the top edges inside the bubble cavity to also seal any bare metal as best you can. I drip in thick paint a few times to make sure it's proper coated. Done this to a car 20yrs ago and it's still like new.

got some painting done last night.
Not too shabby in epoxy primer if you squint, cant wait until some high build goes on.
Next job will be to undercoat the front inner wheel wheels so the guards can be put back on.