score:6
Your layover is normal, it is well above the minimum connect time of one hour.
There is no immigration control for international-to-international passengers (except those going to Ireland). (But you will pass through a security check.)
You will not need to collect your luggage, it will be checked through to San Jose.
BA will reroute you to San Jose if you miss your connection. There is only one flight per day to San Jose, so your options may include indirect flights on their partner American Airlines. You might also be able to take one of the BA flights to San Francisco, which is within driving distance of San Jose.