I too recommend the Shangri lal, nice big rooms especially compared to the Hyatt and buffet food is very good. Hotel on the whole is clean, quiet with vey good staff. I bookeda standard room at £90 a night last year, prices seem to have gone up now at £150 a night, which is surprisingly high!
If you do not mind staying further out then the 5* hotel Kempinski is best value for money but a good distance out of central delhi, i paid £180 for 3 nights with buffet breakfast included last year and airport transfer. Have used hotel cars at both hotels, basic car is about £10 an hour with a driver who takes care of you, more expensive car is more cash.