Off to Cardiff Friday for a day n stop over.

Anyone recommend a decent restaurant (Not Italian/Indian/Chinese).

a quirky bar or two?

Somewhere elegant to have a dance and a GnT.

Anything else can't miss for the day?

Somewhere elegant to have a dance and a GnT.

LOL. This is Cardif you're talking about. You've never been to Cardiff before, have you? Am very tempted to suggest the Old Arcade pub, but they'll only let you in if you're fully DJ'd up and your other half is in a ballgown.
It's difficult to recommend somewhere to eat without knowing exactly what you're after and what price range. My rule of thumb is never to go to a franchise or national chain. The Armless dragon, Le Gallois and The Old Post Office all seem to get good reviews but are pricier. I like the Old Post Office myself (it's in a suburb of Cardiff called St Fagans) and next door there's a reasonable pub where you can sip a pint beforehand. While you're in St Fagans, the Museum of Welsh life is a bit of a must for any visitor – they've taken historic buildings from all ages from all over Wales and rebuilt them exactly as they were withing the grounds of St Fagans. Another good place to eat is "Bully's" restaurant run by a guy who's a bit of a legend in his own lifetime. It used to be located in Llandaf but, since I've been there, I've heard that it's relocated. If you're after pub type food instead of a restaurant, the Caesars Arms in another Cardiff suburb called Creigiau is good (good steaks) although it's a £15 taxi ride from the centre. Cardiff's brew is "Brains" and the classic pint to have in Cardiff is Brains SA. We even have (had) our own wine. Cariad wines are produced in Llanerch vinyard near a place called Hensol. I went there a couple of years ago for a wine tasting session and was surprised at how good the whites were. However, I know that the business has changed hands in the last few years. Rumoured to be a Michelin starred chef running a restaurant there now – but I'm not sure of details. Lots of clubs and bars in the centre – best bet is to simply wander around. Check out the arcades too if you're simply wandering around and looking at shops. If you're going slightly out of town, check out Cardiff Bay – lots of restaurants, bars, comedy club and the Millennium Centre (worth checking if there are any tickets for shows). There's also a comedy club in town between the central station and the Millennium Stadium. Top of your list has to be a tour of the Millennium Stadium – sacred ground. It's where Gods play rugby, but like to tone down their game and lose a few times to make it a bit more exciting.
Oh, and Cardiff girls are famously chaste. They usually hang around in a place called Caroline Street after evensong.

oh you'll be needing one of these:

Oooo memories I would love to move back to Cardiff! oh well 5 day weekend there next weekend and then another week there 2 weeks after that. that'll have to do for the time being!! lots of biking whilst I'm home. sorry can't help with restaurants and stuff since I haven't lived there properly 13 years.

Try the brewery quarter. There's a nice pub called the Yard. The mixed burger platter is great. There's the usual like Chiquito's too. The 10oz gammon steak and eggs in Bar haha's is fantastic. Depends what you want to eat. Tiger Tiger isn't bad for grub either. No idea about dancing though I don't live in Cardiff I work there though so it's all lunch times for me.

However, in answer to your original question, I'd get suited up in your best dinner jacket (the white satin ones are all the rage for the gentleman about town this side of the bridge these days), maybe a cheeky little opera cape and cane for that certain je ne sais quoi. Make your way to the Old Arcade pub (where they usually have a string quartet playing most evenings) and tell the gentleman at the door that you're English and have come for a G&T and some dancing. When he's finished wiping the tears of appreciation (at seeing such a finely suited gent) from his eyes, I'm sure that you will be welcomed in, maybe with an announcement over the PA system, if you're lucky. You will find the locals most friendly and accommodating. It will be a night to remember.

Cardiff……happy memories of Metro's night club…

Can't say I reccommend the dinner jacket and cape for the old arcade. Felt terribly out of the clique when I went in such attire. All the gentlemen about town are wearing smoking jackets and cravats when I went and, as such, didn't get an invitation to take port and cigars in the private humidor at the back of the establishment. Social Suicide! 🙁

@Twin
You, Sir, are a philistine! Next you'll be telling me the barman sommelier has stopped wearing a monocle!

Depends how much you want to spend but i've had very good meals at a few places in the bay and particularly Mimosa Kitchen & Woods Brasserie (fairly pricey but excellent). Bayside Brasserie is also supposed to be very good but I've not eaten there and a new Miller & Carters steakhouse (by the Red Dragon Centre).

In town there are the usual chain choices and a few smaller chains such as Zero Degrees. Not sure what else there really is in terms of independent stuff that isn't Italian, Chinese or Indian though.