Onoff

He was I believe schooled in Kent, God's own county.

Usually your hardwood sill is put in as part of the door frame. Traditionally the jams fit into the sill as tenons. The galvanised weatherstrip extends into the jams. Like this. Why not fold up a bit of aluminium sheet to go over the softwood "sill" that's there, then add a modern, all singing threshold strip on top of that?

I have my Skip Diving badge!

You really want a hardwood sill there as it'll take lots of weather and abuse. You could graft a hardwood bit on the front I suppose.....

You can get them combined as a threshold bit then a weatherstrip: https://www.wickes.co.uk/Wickes-Threshold-and-Rain-Deflector-White-838-mm/p/203002 Or put a traditional wooden bit on the door to oversail a modern, sealing threshold. Search the Stormguard stuff:

Yes. Because too you have a grooved front you might want to silicone a weatherstrip on above something like this below: https://www.google.com/search?q=inward+opening+door+threshold&client=ms-android-motorola&prmd=sinxv&sxsrf=AOaemvJTOQkB52qwZ86TFu9Nd1m7j6ziKw:1632083566354&source=lnms&tbm=isch&sa=X&ved=2ahUKEwiz2dyJ8YvzAhUdDmMBHWIGDykQ_AUoAnoECAIQAg&biw=360&bih=512&dpr=2

A few on here have Bora downdraft extractors I think. Search "Bora".

Well you have been busy...

If you get a plain, IP6x rated box and drill the gland holes yourself, you can arrange the 2 banjos so they "meet" and you can use x1 6mm brass bolt. Take an earth fly lead off that with a ring crimp. Just use Wagos inside to connect everything together. Sort of like this, bits grabbed at random in the shed:

I think we've established it's jam and cream...or is it cream & jam? They can get funny about that I believe.

😱

For a shower tray? Good luck with that.

I thought it said challenged dad... 8-10 years seems a fair estimate for this job.

Stick a couple of bits of 1" thick scrap wood between where the gates meet whilst setting up the second one. Tape it on temporarily etc. Leave in there whist the second post is setting.