I asked about agency staff a few months ago for a big job I had on and got a good reply from Ian Griffiths, hopefully he doesn't mind me passing the info. onto you.
He wrote
In a previous life I employed upto 60 agency workers a day. Bearing in mind that I was a major customer it is worth noting that on a bad day we could have 15% no shows and untrained replacements sent in (often without notice or request).
Over time we ultimately filtered the good ones out and went on to directly employ many of them. Some even moving into admin and management roles.
Rather than waflle on any more I would say that you will be on a loser employing temps to help with this job. I say this for the following reasons: -
1) You are not the type of customer that agencies will respect (Too small, unlikely to give them much in the way of repeat business, etc.) although to your face they may well be all smiles, remember that they are sales people.
2) As a result of the above you may not even be able to get an agency to supply.
3) If you do get one to supply then the odds are you'll be getting the 'dreggs' that no one else wants (unless you are very lucky).
4) You will be paying a premium as not only the wage(s) but the agency mark-up. Have you built this in to your quote?
5) You will have to carry out a full induction (H & S included). You will also have to check with your insurance that you are OK to employ.
6) You will be paying from the place that they report to work. If this is your home / office you will be paying an additional 2 hours wages just for their travelling time.
I think I could probably go on for ever but I am sure you get my drift.
In summary, agency staff can be a great asset in the longer term, even for small companies. It does however take time building a strong relationship with any agency so that you only receive staff of the quality (or as near as possible) as required. It takes a lot of time and effort to do this properly so under the ciscumstances I would not recommend this as a option for you.
