I'd go for something like this if you can afford it:
http://www.zooplus.com/shop/dogs/dog_cages_carriers/carriers/plastic_cages/129675
Bit more space but also both top and front opening, makes it much easier to get buns in and out!
My cats have a huge transporter on wheels, it's a complete godsend as I don't have to carry it and Geoffrey gets very claustrophobic in a carrier and it is big enough that both cats can share it and he can sit right up. The pair of them sit and peer out the window on the way to the vets now :lol: