I live in Romania so very often go to Budapest for different problems. Last time I was there in July 2009 and I visit 3 hobby shops and the situation is like this:
1. Játék és Makett Centrum, 1097 Budapest, Gyáli út 31/b, www.jatek-makett.hu
It's sort like a warehouse, half toys and half kits.
They have kits from Italeri, Revell, Zvezda, ICM, Trumpeter, some Tamiya and Hobbyboss, lots of Dragon, you could spent there many hours, there are thousand of kits, many accessories and the guys are very friendly. Really a place to go and spent some time and money.
2. Modell&Hobby Kft, 1135