if your fairly confident/competent then something like this you could do yourself,they only cost a few pounds each,im sure somewhere on here there are detailed instructions on a how to do.
the object of airbricks is to give ventillation to the sub floor,i would recommend the plastic 9x6 louverd vents (they are more efficent).
you may feel this is above your limits,so if this is the case a decent handyman should be able to do this for you,or a builder will have no trouble at all,unless they find unforeseen problems.
hth a little.