We did a sponsored ride along sustrans hadrian wall route. We had a similar number of bikes. From memory we got about 20-25 bikes in the LWB Sprinter (4.3m long) and the rest went in a pickup we had.
The sprinter wasnt loaded up in any scientific manner so i presume more could have fitted. They were just leant against each other and none of the height was utilised. Would people be happy at stacking them on top of each other. I would think not.
If you were in cumbria i would offer to help as i have demo vans which would do the job.
Anyhow good luck
