Collyer Bristow corporate finance partner Gary Withey led the team on both deals, alongside associate Ragavan Arunachalam.
The acquisition will provide Avia with access to new markets while improving its own product functionality.
The AIM admission will raise money for further acquisitions in the healthcare market.
Collyer Bristow acted for Avia on its admission to the Plus market in 2007. However, an attempted entry to AIM failed in January 2009.
“It’s a real green shoots story,” said Withey. “The deal was dead in the water.”
Avia chairman Barry Giddings added: “The corporate finance team at Collyer Bristow were truly entrepreneurial in their approach to the transaction.”
Marriott Harrison advised broker Merchant John East on the placement, with corporate partner Simon Charles taking the lead role.
Manchester firm Pannone acted for the Plain Software Company, led by senior associate Daniel Varney.