Singita Boulders Lodge is a good choice. But 2 potential problems: rates at the dozen top-end lodges tend to be USD1000 per person and up (so maybe GBP 1000 is the minimum budget), the bigger problem is many lodges have a 3 or 4 day minimum stay. I'm sure you can find 2 days at your price point but it may take some searching and won't be one of the top lodges.