Good Morning and welcome. I am Dr. Loretta, a licensed veterinarian and I am happy to answer your question.
I am sorry to hear about your problem but this is common. The fleas do not live on the cat...they live in your house and the best way to rid your house of these pests is to use a flea bomb...use this once and then again 2 weeks later because the initial bomb will not kill off the larvae that will come out 2 weeks later. This way you will rid your house , your roommate and your cat of these fleas.
This LINK explains the type of Bomb you need. You will have ot take the animals and leave the house for 4-6 hrs and then return.
Does that make sense to you?
Please let me know if you have ANY other questions. My goal is to give you 100% satisfaction and if you are not yet satisfied, please Reply so I can clarify for you
Sincerely, XXXXX XXXXX
Where can this be purchased in the UK?
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I wonder whether you're ok with continuing to wait for an answer. If you are, please let me know and I will continue my search. If not, feel free to let me know and I will cancel this question for you.