Easy tigger, order several meals and freeze some down. I have been doing this for years. Another excellent one I have just discovered is called Ruby Spice, at 125 Beulah Road. They do a particularly interesting side dish called Bengal Potato, which when served with Murgh Naga chicken (all laced with green naga chillies) and garlic rice makes for a wonderful evening meal.
Croydon Curry Chef of the Year 2004.
(Incidentally, I am sure that in practice if you order a single meal under �10 they will waive the delivery charge, particularly if you are very close by and ask them nicely. I always buy about �25 of curry and tip the driver well)