High Average - JSP 905 - surely you qualify for the Tier 1 lump which maxes out a 2x pensionable pay?
135.2 A member who receives a Tier 1 ill-health discharge after they have achieved at least 20 years pensionable service and reached the age of 40, will be eligible for their standard EDP (lump sum and monthly payments) or a Tier 1 lump sum (not both) as determined by the scheme manager. The policy intent is that the individual should receive the better of the two.