I always stay at the
Hotel Atlanta on Wahringerstr.
Very friendly staff, reasonable prices and a great bar (Shooters) downstairs. It's within easy walking distance of the centre. Takes about 7 minutes or so to get up to Schottentor (just past Charlie P's) and then you have a nice stroll either through to the centre, around the ring or down towards the Donau canal. If the Heurige at Grinzing are your thing then the tram goes from very close to the hotel. "Not too expensive" is a very relative term. You can of course find cheaper hotels, but this is always my residence of choice.