Hi Hardcastle, just had a quick look at your facebook page and there are some pretty basic things you can do to boost your facebook page and likes, but first off the big questions are:
a) What are you looking to achieve from Facebook (Do you have goals)
b) What are you prepared to give in order to achieve your goals (Time/activity/offers etc)
Have you ever thought about paid advertising or simplifying the message?
In my humble opinion to get the most from social media you need to follow 2 basic rules.
1. Be consistent
2. Be social
Everything else will come if you follow these rules, also try give something that engages people better, ie if you post a before and after image ask people to rate the work out of 10, ask customers whom you have worked for to like , review and comment on your work.
I used to run a large cleaning business and currently run a small search engine marketing agency, if you want a chat I have a couple of guys who specialise in social media and I can get you chatting with one of them, feel free to call me on 01332 987575
Geoff
PS I have also liked your facebook page