What license do you have?
I think all 17 seater minibuses will be over 3.5t so you need a pre-97 license, with a pre-97 license you can drive a 17 seater including the driver. But post-97 licenses you are limited to 8 passenger seats plus the driver, not forgetting your license won’t cover the weight. If you update the recorded number of passenger seats to 16 or less you can drive a minibus with over 8 passenger seats if:
i. the vehicle is used for social purposes by a non-commercial body but not for hire or reward
ii. the driver is aged 21
iii. the driver has held a car (category B) licence for at least 2 years
iv. the driver is providing the service on a voluntary basis
v. the minibus maximum weight is not more than 3.5 tonnes or 4.25 tonnes including any specialist equipment for the carriage of disabled passengers
vi. if the driver is aged 70 or over, is able to meet the health standards for driving a D1 vehicle
Also, minibuses are rubbish for camper conversions as all the glass makes them freezing cold/boiling hot depending on the weather condition. Insurance will also be practically impossible to find with the camper modifications along with the number of seats.
Edit: Do you need all 10 seats? You can get crew vans with 7 seats, 3 up front and 4 behind, probably an easier choice plus you just fit windows where you want them.