Gas Engineer for New Boiler Installation Recommendations Needed Please.

My gas combi boiler is on its last legs after about 13 years so I'm hoping for some recommendations for a trustworthy gas engineer who could do a new install in Hackney. I've looked online but, what with fake reviews etc, I just don't know who to trust to do a decent job without ripping me off. My friend recommended two people, but they still haven't gotten back to me with quotes after three weeks. I was also advised to look on the app Next Door but the app want too much personal information to sign up and log in. Any suggestions? Even if you don't have a recommendation, any advice on how to look for a safe person/company would be welcome. Thank you.