Cat sitter 5 days over Xmass

Did you try contacting the 2 who have announcements in the small ads section under pets?

We're not travelling this year so I could easily pass by once a day if you like- 15 euros per visit. I'll provide them with their food and water, some cuddles and a brushing; Plus send you pics via mail while you're away. If you're interested send me a response here :-) Thanks and have a lovely holiday!

Hello,
My son (17)would be quite happy to take care of your cats while you're travelling. He's a regular cat-sitter for our neighbours' pets and would love the opportunity. Plus we live in Schaerbeek.
Greeetings

try catiliscious web site - they provide care and attention by pre-registered pet lovers... as often or as little as you want...

For 15 EUR/day you can take your cat to a cat hotel. It will be in its own big enough closed space, they'll provide food and litter and let it walk around and socialise with other cats daily. Plus, they will be there if your cat needs a medical or other assistance.
I can recommend a hotel in Etterbeek but I am sure there are some in Schaerbeek too.