i would go for a 24L, 50L and 70-200L. best setup. no point getting a 135L if your gunna get a 70-200L especially f2.8 version. that lens is PRIME quality no joke mate.
And yes, 5dmk3 is £600 expensive. £2400 max. i hope it goes down to £2k end of the year.
I use my 70-200 IS mkI quite a lot, I could probably justify upgrading it to the mkII but whilst the mkII is sharper it's not going to make a great deal of difference to my photography. The 135L seems to be a special lens and I feel that I just need to get one to experience it, buying and selling second hand will probably just cost me the postage which would be cheaper than renting one!