I need to re-coat the decking in the garden. I did it last year and the finish is horrible. It went on like thick paint, rather than clear varnish (my fault) and so I now need to do it all again

I've had some success with the jetwash. Most of it has thankfully faded and it appears to be coming off with the Karcher. It will take ages though, doing it like this, not to mention the vast quantities of water used!

Is there anything on the market that will remove it? I'm thinking something like paintstripper. Either that or an industrial size sander I think! 2010 MY Vogue SE TDV8 3.6 Stornoway Grey- fully loaded

I'm doing the same to mine and decided to sand it down with a rotary sander back to bare timber, if that starts to take too long, then hire a floor stripper. I won't stain mine again, just oil it. Current MY2020
Gone: 1 x L405 and 2 x L322's

I do the same pointless exersise every year on a rather large Deck & Summer house I built 9 years ago:

1. Jet Wash off the winter slime.

2. Replace any rotten boards

3. Paint another coat of B&Q Deck Stain over the top.

Takes a whole day day to finish but the result is surprisingly good if not a little "Mottled" but it last to the following winter thats all....

Click image to enlarge

If you are going to have a deck use Western Red Cedar as it does not need stain or oil it just fades to a lovely silver grey. All I had to do to ours, in ten years, was a quick wash each spring to take off the winter slime. 2010 3.6TDV8 Stornoway Grey/ Black interior - gone
2005 4.4V8 (M62) Bonatti Grey/ Parchment interior - gone
1998 4.6HSE Blue/ Cream interior (can't remember exact colours) - gone
1977 White - gone (should have kept)

I stained mine every year like Gaz. It started out light oak, but each year I used a darker shade to cover any blemishes and now it's ebony! Hence the complete strip and start again.  Current MY2020
Gone: 1 x L405 and 2 x L322's