Clever or un-intended its brought them a lot of exposure for the investment made.
Definitely clever.
If you look at their entry at companies house the vast majority of their business in done in UK.
The parent company is French, so a year in the Prem will have given them global exposure, especially now every games is broadcast.
They also say that their business is driven by installers, so the boilerman mascot would promote at the very heart of their customer base.
I would say that there is a very distinct correlation between our embarrassment & the upturn in their business.
Additionally football is essentially a winter sport, just when you need heating.