Eric Partridge, A Dictionary of Slang and Unconventional English (1984) offers two definitions of "tip up," but neither seems at all relevant to the quoted situation:
tip up. To hand over, 'fork out', esp. money: low:—1859 ... 2. To hold out; low and nautical:—1887. Esp. as in Baumann, tip up your fist (or fin), reach or give me your hand!, shake hands!
As Barmar says in a comment above, the context of the phrase "tips up" in the OP's question indicates that its intended meaning is "shows up." However, if this usage is idiomatic in the UK or elsewhere, it hasn't yet become widespread in published print writing. Google Books searches for the phrases "tip up at," "tips up at," "tipped up at," and "tipping up at" uncover exactly two on-point matches. From Fiona Parashar, The Balancing Act (2005):
People will always look upwards for direction, and if that upwards is constantly changing it ids confusing and can cause people top become disconnected from the reason they turn up to work every day. Then it really is an awful virus, and it does slowly kill people off mentally. Unconnected to the meaning of their work, to their new role, or their new goals, the energy ebbs away, until the shell of a human tips up at work each day and emptily carries out its task. The rich dynamism of a challenging and engaged worker suddenly seems a rare thing.
And from Miranda Glover, Soulmates (2007):
The war in Iraq rumbled on, but now Israel was fighting Hezbollah in the south of Lebanon, too, and the region seemed set for a period of even greater instability, of civilian carnage. Will followed the news eagerly, seemed energized by the escalation of violence and spent countless hours with Ralph, discussing the latest attacks, calculating their impact, economically, environmentally and, most significantly, from a humanitarian perspective. He was tipping up at Polly's place later and later at night and she noticed that he was drinking more. Many days could go by when he no longer mentioned Emi.
I ran a second set of searches for "tip/tips/tipped/tipping up in" and found two additional matches. From Robert Ashton, Waking Up in London (2003) [snippet]:
Then he tipped up in London. A straight job here, drumming in bands there. He worked on the Observer, then a band looked like it would work out. But it didn't. 'When I came to London in 1983, I found myself playing a lot of straight-ahead jazz, ...
And from Gabrielle Mander, Just Write: The Virgin Guide to Telling Your Story (2007):
This zone had not been her intended destination when they had turned the time key that morning. ... However, something had evidently gone awry. She had intended for them to spend the day in around 2050, when the emissions had at last been cleared and the atmosphere was fit to breathe again. She had not expected to tip up in 2020, when the world put the chaos back into chaos theory.
Notwithstanding the Americanized spelling "energized" in Glover's excerpt, Soulmates was "First published in Great Britain," according to the book's copyright page; the other three books appear to have been published only in the UK. So it seems that "tips up" is a British idiom of fairly recent vintage (all four Google Books matches are from 2003 or later) that can be used with at or in (and possibly other prepositions) and has the meaning "shows up" or "pops up."