Wow, thanks for all the replies! Lots of information for me to injest, I really appreciate it.
I can definitely start to put some of the suggestions into practice...I checked my vacuum too and it does have a hepa filter, so that's good. We have carpets throughout our house except for bathrooms and kitchen and I can't see us replacing everywhere with wood, though maybe partially over time. At the same time I will be more diligent with cleaning and try to keep Bilbo off our bed. We do shut him downstairs at night BTW, so he doesn't sleep with us.
As I stated, I am already on a nasal spray very much like Flonase and have got relief apart from blocked ears and catarrh now, I might try some antihistamines too. I do notice I'm worse after cleaning the litter tray so will try different litter and get hubby to clean it more often instead of me. I may also ask my GP about allergy shots, thanks to those who suggested them as I never would have thought about the option.
I'm going to have to tough it out as I won't be getting rid of my Bilbo (yes I love LOTR Manny!). I hope though, that my allergy gets less rather than worse over time, as some of you have mentioned. BTW I laughed at the idea of me bathing Bilbo...yeah, like he's going to allow that! I don't want to risk life and limb! I have however discovered that I can get wipes to run over the cats fur to help remove allergens so maybe I could try that too.
Texstyle you asked about a screened porch and I'm afraid we don't. I mean we do take Bilbo out on a harness, but it's only an hour at a time. Plus I'm at home most of the time :(. I couldn't risk letting Bilbo out though due to a nearby very busy road.
Thanks once again all!