I am unable to find cream cheese in my locality and one or two brands which I can find are too expensive. Could you suggest a replacement for the cream cheese?
Cream cheese frosting is a traditional icing for red velvet cakes, however for the Red Velvet Cupcakes (from Kitchen and on the Nigella website) Nigella makes a buttery version that is half butter and half cream cheese. If you can't find cream cheese easily (and note that in the UK it may be labelled as "white soft cheese" but is likely to be the same product) then you could use mascarpone as an alternative. However it is easy to beat macarpone too much, causing it to curdle, so be careful how you handle the mascarpone.
If macarpone is also difficult to find then we suggest just making a regular buttercream by using all butter (ie 250g butter) rather than half butter and half cream cheese. If the buttercream is too stiff to spread then beat in a little milk, 1 teaspoonful at a time, until it is a spreadable consistency.