Woofgang is right, contact companies and see what Qualifications/ affiliations and Pre-Qualification requirements they are looking for in a company when tendering out.
Could they meet with you to discuss perhaps going on their approved contractors list for future projects? If so, you would probably have to agree to a schedule of rates and get your H&S doc's in line with their requirements.
Think out of the box, for example, rather than job-for-for, if it's joinery you do - Have you thought about approaching High street store companies to enquire about Shop-fitting? Is this something you could do? (e.g. do you have a cad engineer to do drawings, would you be prepared to out-source to get decorator's/ electricians on your team to create a full shop-fitter package, Do you have the resources to create and store bespoke counters/ units/ doors and would you be able to submit planning applications to local council for building control etc?).
Think as big as you like - local businesses to get a portfolio together, have a good working relationship with your subcontractors then approach a bigger company. The sky is the limit really.
Or, if you don't fancy shop-fitting, how about approaching large company Head Offices and try to become their company of choice for any HO site improvements? (That can lead to a very cushy income).
Hope this helps and all the best with the development of your Co. :-)