This answer is assuming you have a through ticket from St. Pancras to your final destination in France/Belgium/Germany/whereever. I am not certain whether this also applies to a journey made up of two separate tickets unrelated to each other.
For trains that operate within the European Union under the directive 95/18/EC (that is basically any train except for regional, urban and suburban transport plus the car shuttles through the Channel Tunnel), the regulation (EC) No 1371/2007 lays out the minimal conditions under which a passenger is eligible for refunds. (National laws may expand the conditions, i.e. to allow for refunds even in case of shorter delays.)
Chapter IV, Article 17:
Without losing the right of transport, a passenger may
request compensation for delays from the railway undertaking if
he or she is facing a delay between the places of departure and
destination stated on the ticket for which the ticket has not been
reimbursed in accordance with Article 16. The minimum compensations
for delays shall be as follows:
(a) 25 % of the ticket price for a delay of 60 to 119 minutes,
(b) 50 % of the ticket price for a delay of 120 minutes or more.
The calculation of the period of delay shall not take into account
any delay that the railway undertaking can demonstrate as having
occurred outside the territories in which the Treaty establishing
the European Community is applied.
The compensation of the ticket price shall be paid within
one month after the submission of the request for compensation.
The compensation may be paid in vouchers and/or other services
if the terms are flexible (in particular regarding the validity period
and destination). The compensation shall be paid in money at the
request of the passenger.
Thus, since you arrived at your destination more than 60 minutes after the intended arrival, you are entitled to a compensation of 25 % of the ticket price of the single ticket. (12.5 % of the total ticket price in case of a return ticket. This is specified amoung other things in the part I left out.
Unfortunately, I cannot find the relevant Eurostar web page where you would be able to directly claim compensation for the delay. I suspect that you should submit your claim to whichever company you bought your through ticket from. Ideally, a ticket office will provide assistance, but writing or emailing the company with a copy of your ticket attached should also work. In case they refuse to pay, friendly remind them of the respective paragraphs.