OK!

[Efemera]

After a week of rain in the Lake District and trying to find a nice waterproof jacket I've come to the conclusion I'll have to make my own... there's very little in the outdoor shops that goes over a size 18.. which is fine for the top but alas not enough room for the rear end. I have a nice waterproof Sea Salt jacket but want something a little more sporty.... any suggestions for patterns and fabrics?...it has to be lightweight to put in a back pack( that's a whole other story!)

[Efemera]

Love this....but it's in Knipmode 2009,

[Starryfish]

 >:)How about this one from Shelby patterns in Finland?
https://www.shelby.fi/product_info.php?cPath=402_39_21&products_id=165

They also sell waterproof fabric and tapes etc,although they are really expensive. I tried making a waterproof jacket but really struggled with taping the seams and gave up in the end. There's nothing worse than a leaky neck seam.

Or the Closet Case Anorak- https://store.closetcasepatterns.com/products/kelly-anorak-jacket-pattern. The downloadable pattern is $14 though.

[Ohsewsimple]

I feel your pain Efemera.  I had to go looking a while ago when we were off to Norway.  Sizing is all over the place.  I ended up getting a very lightweight one from Mountain Warehouse.  Of course, the heavier weight one I also needed to replace my 10 year old coat didn't fit!  Same size as the light one.  . So I ended up with another from Karrimor.   I didn't have time to make anything but if you want to go down that route try
http://www.pennineoutdoor.co.uk
And
https://www.profabrics.co.uk

They have patterns, fabrics zips and all the stuff needed for making outdoor wear.