Hi Anita
It's generally cheaper to book your connecting flights through us as we have negotiated special rates with the airlines. Unfortunately, I don't believe that we offer connecting flights on our Kenya holidays so you will need to make your own arrangements for getting to Heathrow this time.
I had a quick look at BMI's website and at the time you are travelling they are offering flights for about £65 (£25 to Heathrow and £40 back to Belfast). But I would shop around a bit for the best deal.
Kind regards,
Olly, your editor