Having got away with something before isn't a justification for doing it again. You were not unlucky to be caught this time, rather you were lucky not to have been caught on previous occasions.
For future trips, I would recomend buying a CIV▸ "Eurohigh saver" to "London International". It will cost about the same as a saver, has no restrictions, includes a cross-London tube journey and if FGW▸ are late and you miss your connection, Eurostar are obliged to put you on their next service at no extra charge.
I'm not sure whether eurotraveller visits this site. Maybe an idea to also post this on the
MTLS▸ forum, given that it is a direct reply to him?