Where are all the bees?

I have a garden full of bee-loving plants but no bees.  I have probably seen 3 bumbles and a dozen others since March.  I should be seeing (and hearing the buzz) every day now, but no.  Even though a huge Rosemary bush is in full flower.  Even though my Cotoneaster is in full flower.  Even though nearly all my flowering plants are "singles" (bees don't like doubles), even though this was a brilliant year for dandelions;  still no bees.  I have a yellow clematis (Bill MacKenzie) which is just now coming into bloom and that will have hundreds of flowers.  Perhaps they will come for a feast on that?

Red tailed bumble queen

I don't use weedkillers (except Roundup gel for dandelions in my paths, and even then I cover with a flowerpot after application until the dead plant can be removed).  I have bee hotels for mason bees, but don't see many.  I used to see loads of bumbles, but not this year.  It's so sad not to see the little workers out and about - but that's just sad for me.  The worry is where are they at all?  Someone told me this morning that if they are out at the rape fields this does them no good in the winter as the rape honey sets too hard for them to use. 

Here's an interesting article from a local (Dorset) magazine a couple of years ago.  Still relevant.  I hope they will be off the rape and back in my garden soon, I miss the buzz.