Outfit for a 'do' in a marquee this weekend?

[MsFogi]

Stylish mners - what sort of thing would you wear to a 'fairly casual' drinks party being held mid afternoon in a (supposedly heated) marquee this weekend. Weather forecast says 9 degrees and 40% rain.
I hate marquees!! I suspect wearing my skiwear is out of the question?

Ooh! This is the one occasion where I would be prepared to wear a jumpsuit. (With thermal layering underneath!) It would feel just like skiwear, while being cool and stylish.

D’you have a budget? What size are you? And are you aiming for wallflower or centrepiece?

Jeans, boots, nice top, nice coat.

This would be warm …

www.matchesfashion.com/products/Raey-Patchwork-suede-jumpsuit-1339097

But this is cheaper:

www.stories.com/en_gbp/clothing/jumpsuits-playsuits/product.belted-collared-jumpsuit-purple.1042299001.html

Thanks for the replies so far. I am hoping to use something from my existing wardrobe (which is bulging with loads of pretty much unworn stuff) so wanted a steer on what 'sort' of thing people would wear (although I may end up buying something new of course ).
Jumpsuits are a good call (will have to double check I can do them up again after going to the loo!!). I wear jeans all the time so I think I am going to have to look like I have made a bit more of an 'effort'.
So far it looks like people think that the dress code 'fairly casual' really does mean pretty casual - I wasn't sure!

What is the drinks party for? Is it a wedding reception - in which case I’d want something in a casual shape but prettier colours than office wear - or something else?

Hiring a marquee isn’t all that casual …

@TottersBlankly

What is the drinks party for? Is it a wedding reception - in which case I’d want something in a casual shape but prettier colours than office wear - or something else?

Hiring a marquee isn’t all that casual …

It's birthday drinks

Sorry @TottersBlankly but those 2 jumpsuits are truly revolting imo.

@MsFogi. maybe start with a suitable coat and shoes and then work from there?

A dress and boots with a coat/jacket that can stay on or be removed according to the heat levels would work.

skinny jeans, nice top, leather jacket and thermals. And 2 sets of socks.

Jumpsuit and thermals is probably best bet.

I'd take a pashmina or scarf or something as well

We’ve rarely agreed on an outfit choice over the past decade, Remus! I doubt either of us has ever found this a problem in real life - so it’s all good.

I suspect we're very different in terms of age and shape, Totters. I don't recognise your name, so don't recall disagreeing before, but if I knew you in real life, I'd definitely admire your outfit choices, even if I wouldn't wear them myself!

I name change all the time. But you always hate my choices!

Generally I’m simply responding to whatever criteria the OP has set out, searching shops I use myself - but the things I link are rarely things I want to buy. Because my criteria would be different.

What’s most frustrating is when I invest half a morning on wedding guest dressing for someone who ‘doesn’t want the usual thing’ - and then they send for a Bombshell dress … (It seems pointless to be annoyed at someone else’s exercise of their free choice, especially when people look perfectly fine in them. Just wouldn’t wear one myself.)

Birthday drinks - I would personally wear a skirt, thick tights, knee high boots, thin jumper or top and a jacket / chunky cardigan in case it's not so heated. But I'm nearly 50

I would avoid jumpsuits all the time to be honest, nightmare for the loo

@TottersBlankly

I name change all the time. But you always hate my choices!

Generally I’m simply responding to whatever criteria the OP has set out, searching shops I use myself - but the things I link are rarely things I want to buy. Because my criteria would be different.

What’s most frustrating is when I invest half a morning on wedding guest dressing for someone who ‘doesn’t want the usual thing’ - and then they send for a Bombshell dress … (It seems pointless to be annoyed at someone else’s exercise of their free choice, especially when people look perfectly fine in them. Just wouldn’t wear one myself.)

For what it's worth, I'm not a fan of Bombshell either!

Flares, boots, nice long sleeve top

Pattern somewhere on outfit, be it trousers or top