I have to back up binkie on this one - am trialling nannyjob but have had some real hit and miss candidates, and the 2 agency candidates have turned out to be the better ones.
Unfortunately 1st 2 agency candidates were useless so also been burnt there - but have switched to using agencies listed on bestbear -
if you CAT me I can send you their details.
Re horribly complicated situation (was in similar position last yr), I have found that the best thing is to offer hours & salary upfront to the person that you click with most.
I ended up employing nanny more hours than expected but this worked because I had never offered more than I could afford. It also gave me loads of time for studying, which meant that w/e's were all mine, and got course finished without year end stress.
If you employ someone who is open to say, having half day off come Sept to do family shop & for you to spend time with little one, but will work the hours you need now, you are probably on to a winner.
Most childless, sought-after nannies prefer Mon-Fri sole charge as much as possible, so I had to modify my requirements to fit the best person for our family. This gives better peace of mind than looking for a person who will miracously be flexible and affordable.
Obviously there are other options, I am just speaking from my own experience. HTH.