Visa Advice - Uganda

Hello

I am from the UK (UK Passport) and will soon be going to Uganda. I have
been checking advice for Visas and I am getting conflicting information.
Can someone please tell me, if when I get to the airport in Kampala I can
pay the money and obtain a single entry visa there, rather than obtaining it
before I go. I fly into Kampala via Nairobi but I wont be getting off the
plane there. I will be leaving Uganda after about 10 days by road into
Kenya and then Tanzania.

I appreciate any advice

Dan