The OP asked for "a quick way", so here is my one-liner:

perl -ape 'substr($_,0,length $l) =~ tr/ / /c if $F[0] eq $l;$l=$F[0]'
+ <<END
GEORGE 21
GEORGE 45
NICK   12
PETER  27
JIM    18
JIM    87
CHRIS  33
END
[download]

prints:

GEORGE 21
       45
NICK   12
PETER  27
JIM    18
       87
CHRIS  33
[download]

On review, I see that my solution is practically the same as CountZero's $saved_name algorithm, but needs no pre-calculated size for the 'name' field.