San Carlo is my favourite place in town (http://www.sancarlo.co.uk/) in deans gate. There is also Grill on the alley , also in deans gate. Restaurant bar and grill near deans gate is also an excellent place. But I highly recommend San Carlo, gives you a chance for celebrity spotting too :)
Grill on the Alley is an amazing, friendly, fun place to eat if you have a thing for great quality steaks, coupled with a wide selection of quality wines. Went for my birthday last year and had one of the best meals of my life!