I am a gas safe registered engineer and I like getting something for 'nothing'. I figure that with energy prices rocketing, as they are a collective monopoly given free rein to charge whatever they like, I should invest in getting free electricity for a fixed outlay. That way I can get a far better return on my money than giving it to an 'Independent Financial Adviser' who charges so much you end up with a negative-going investment.
Go to an organisation that has a recommendation. Personally I am a domestic gas engineer. My van has no contact details on it and I do not advertise. All my customers come from personal recommendation: I don't need anything else.
For solar electric I can highly recommend Redmile Energy, who talk sense, not waffle, they surveyed the house properly before giving a quote, offered 3 different quality levels of panel and answered all my technical questions knowlegeably.