Many thanks to all for taking part. Here’s a summary of the contributions. Quite a fun list.
A - second-rate, airhead, hubcap (or H)
B - bump-start, butthead, bighead, head-butt (or D)
C - cooktop, crackhead, clubhead, reactor core
D - godsend (-> god’s end), Land’s End, rearguard, the back of beyond
E - sweetheart, centrepiece, dovetail, endgame
F - offending
G - midnight, legend (or L)
H - hothead
I - midpoint
J - jump-start
K - weekend, cocktail, bookend, kickback
L - midfielder
M - masthead
N - nightcap, detention centre
O - photo finish
P - apple core, midshipman
Q - leading question, earthquake’s epicentre, quayside (or Y)
R - redhead, Center Parcs
S - headstrong
T - third-rate, butt-end, midwestern
U - upstart, community centre, fourscore
V - private eye, service centre
W - centre-forward
X - oxtail, bauxite core, fux coda
Y - ponytail, happy ending, soggy bottom
Z - midsized