Replacing Bosch Rotak 36 Lawnmower Belt

[carder1]

Motor runs but blade doesn't so went to B&Q to buy a new belt. Sales guy tells me they don't sell any belts and in any case, they cannot be accessed because special screws are used. However, the belts are available online but some reviewers have had a hard time fitting them. Anyone here had any experience of fitting these belts?

[aeromech3]

I know my Mountfield drum drive belt was a pain, had to un-mount the motor to slip it in.