Nationwide's latest adverts starring a pair of sisters singing ditties have gotten in everyone's heads, for better or worse.

Flo and Joan, a tongue-in-cheek piano and percussion duo, have starred in a series of Nationwide adverts over the past month. One was all about the "Crimbo Limbo", the weird period of time between Christmas and New Year, which they sang while wearing onesies. Another was about their sibling rivalry, a third reflected on how to make a tiny house into a home, and the most recent asks their mother which one of them is her favourite.

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Flo and Joan are, in reality, a pair of Toronto-based British sisters from Portsmouth whose real names are Nicola and Rosie Dempsey. They are both trained in sketch and improv techniques and came to international recognition for a viral hit they had last year, the 2016 Song, seen around 46 million times across different social media platforms.

It begins with the melancholic words: "2016, it's been a time, it's been a struggle. But everything is fine if you're a straight white male muggle." The song then wittily references the beloved celebrities who died in 2016 as well as the Zika virus, Stanford University rapist Brock Turner, the Brexit vote, Donald Trump winning the US presidential election, and a plethora of other unhappy events from the year. They shared a follow-up last month called Have a Cup of Tea (A 2017 Song), encouraging people to have a brew when the news gets them down.

They have also received critical acclaim for their work on the comedy circuits, being named one of the top 10 shows at the Edinburgh Fringe Festival in the Amused Moose Comedy Awards for 2016. They returned to the Fringe for a sold out, well-reviewed show last year.

The duo have also headlined shows across North America and the UK, and will appear at London's Brasserie Zedel monthly until June, as well as at the Soho Theatre and Leicester Comedy Festival in February, with "dark, witty" songs. Their debut album, Victory Flaps, was released last spring.

Performing musical comedy is not the only thing they have put their minds to - in 2015 they completed a 365-day challenge to eat the National Food of the Day every day, documenting it on their blog Little Nibblers.

They haven't won over everyone with the Nationwide adverts, though, not helped by the songs' catchiness – which can grate when you hear them during what may feel like every advert break.

In a Reddit thread last week, referring to the "annoying" Crimbo Limbo advert, one user said: "They only had five days to milk that advert and boy did they. It felt like every channel I switched over to happened to be playing that ad at that moment." Not everyone dived in with negativity though, with someone else saying: "I disagree - it's a good advert compared to the usual bunk we get on TV."

Mumsnet users were not much more sympathetic. In a thread titled "Am I being unreasonable or does anyone else hate the Nationwide singing sisters?" people vented their rage at the ditties, although again there was a minority in support. The women were called "smug" and blamed for bringing "irrational rage". Even a Nationwide mortgage adviser was unimpressed, saying: "I just scream at the telly - just advertise how low our mortgage rates are!"

Several users said they liked the Crimbo Limbo song but not the others: "They didn't need to spoil it. Should have quit while they were ahead," one critic said.

Twitter users are also torn. Plenty of people have tweeted at Nationwide's official account, telling them how much they enjoy the adverts.

But others expressed their frustration at the "painful and annoying" songs.

Still, at least it's not "match day's my favourite day"...