the trainline com

sheffield to luton 13 MAR 15:05 so that means 3 hours
before to arrive at luton 12-13 a clock to arrive

LONDON LUTON to sheffield 2 APR 23:55 after 1-2 am on 3
apr to sheffield,

so what they did,

Outbound Tuesday, 14 February

Return Friday, 3 March
04h 15m, 1 change
12:15 Sheffield (Coach Station)