In use, did this radar provide a lead point in the HUD at which to aim??

Not a HUD, merely a gunsight. Lead computing gunsights adjust for bullet
trajectory based on gravity and aircraft load factor (G). The pilot could
adjust the sight for target range and (sometimes, usually?) wingspan of the
target aircraft (the better to estimate range by). Once engaged, you had a
sight that provided a correct lead solution for a particular range
(typically 800-1000 feet).

With radar input, the range setting is based on actual target range vice a
fixed input, thereby eliminating a variable in what is typically a highly
dynamic environment.

R / John