I wanted to try the new, fast St Pancras Eurostar but I worried that security delays would make it a pain.
As it happens, it was terrific.
Ten minutes in a taxi (with a delightful driver whose wife used to work for Radio Caroline - you'd be astonished how supportive and positive 99.9% of the population is). Five minutes through security.

Then a short wait with a coffee and off - two hours and in Paris at the Gare Du Nord.

The round trip cost was

Eurostar is a great alternative to France/Belgium for Londoners,but the rest of us it's quicker to fly.Birmingham/Paris is about an hour away.
Prices,well you got a bargain there JK,even if you don't look your age;)
Last went on Le Shuttle with a car back in 2002,cost me nearly $400 return,and that was at night!
Like the bit about the taxi driver being supportive,they're normally grumbly old maids in disguise,and yes those who bother to take the time to think themselves are mostly coming round to commonsense.

Hi JK! Just found you here.

I'm also 60 (just over!) and living in Spain. How d'you get your discounted rail fares? I have a Spanish railways Pensionista discount card.