Thanks Simon and Jeff for clarifying about the sort buffers and procedure cache.
The code is working on about 9000 rows each - (x 150 procs) so am rather surprised that I need more than 25Gb cache. Is it important how the data cache pools are configured ?
I've seen some servers configured with tempdb's on tmpfs and a small data cache over it (less than 10Mb)
How would sorting work in this environment ?
Thank again - I'll raise an incident.