Research Councils UK has recently announced the 2010-11 fee and stipend levels, which have increased in line with inflation:
RCUK Announcement (PDF)
The UK Fee Level (i.e. maximum fees Research Councils will support) for 2010-11 is £3,466 p.a.
The National Minimum Doctoral Stipend for 2010-11 is £13,590 p.a.
These are the figures that should be used when costing Research Council proposals which include PhD students, and they serve as a guide for costing student bursaries into proposals to other funders.