My advice would be to read up on natural search optimisation - try this site
Search Engine Marketing (SEM), Paid Search Advertising (PPC) & Search Engine Optimization (SEO) - Search Engine Watch (#SEW)
efforts on optimising your site, will also benefit your ad words hugely - it will improve your quality score. Don't try and bid on words that are not relevant, starting with core words targeted by region and device that will drive your highest quality - to do this you will need to be as targeted as possible even if you think you are bidding on the same keyword, split out the variations and let each have it's own bid price. Its a pain at first, but the optimisation favours more targeted bids.
An example may be "stainless steel fabrication" targeted to leeds area on desktop to set times of day (i.e. not weekends). Even though no one will search on the weekend (just a guess BTW), the more targeted you are, the more you will be favoured when those conditions happen. Don't ever do broad match if you are cost conscious.
You should be able to test these keywords in the engine and get expected volumes. There are other tricks to improve your exposure, such as when your CTR drops too low, Google will stop showing you, but if you recreate the same keyword and terms as a new keyword, it will run a minimum number of impressions again to see your CTR.
Also use
Google Trends
You could always hire a Uni student who is willing to be paid by the hour to do this - or even better - pay him by results, and he can do it from home. Maybe someone who's friedn works in Search Engine MArketing