I don't know how much land or sea based nuclear deterrent the Brits actually have. But you calling them small is a bit naive imho.
The Royal navy has 4 Vanguard class Nuclear Balistic Missile Submarines (SSBN). If you take into account that many tasks like maintenance, crew training and so forth is divided between a relatively small fleet, it is unlikely that all 4 of them are on patrol at the same time.
The U.S. navy has now 14 SSBN (with 2 of them often in maintenance, lasting at least a year) and each sub does about 2.5 patrols a year with them lasting about 3 months. totalling roughly 175 days a year for one American SSBN (2012 figures).
Source:
https://fas.org/blogs/security/2013/04/ssbnpatrols/
There's not much info about Royal navy submarine patrol at all.
But I found an article from 2013 that there have been 100 patrols from Vanguard class SSBN's.
Source:
https://www.royalnavy.mod.uk/news-and-latest-activity/news/2013/july/26/130726-victorious-clyde
The Vanguard cass has been in service 33 years until that point, but only from 2000 all 4 of them have been in active service at the same time. Also you have to consider that after comissionsing, a submarine or surface ship won't get into complete active service straight away, having to complete final tests and thus likely wouldn't conduct a deterrence patrol right away.
The first Vanguard has been commissoned in 1993. (the second in 1995, third in 1996 and fourth in 1999). So only from 2000 4 SSBN's of the Vanguard class have been active.
A Vanguard has between 8 to 16 trident missiles with each up to 8 warheads so anywhere between 64 and 128 nuclear warheads at anytime could hit Russia. That's very damaging. If the Royal navy would have other SSBN's out there, it would be likely that any submarine base would be targeted by the Russians in case of nuclear war, destroying any stationed SSBN. So second strike capability of the Royal navy would be limited.
The Royal navy says there's always 1 SSBN out there, never all 4 at the same time to ensure continous deterrence
https://www.royalnavy.mod.uk/news-and-latest-activity/operations/global/continuous-at-sea-deterrent
If we assume that the Royal navy has constant deterrence and that a SSBN patrol last 3 months roughly, then that means that there's always 1 out but not more than 1 either.
Unlike a few here, I don't pretend to be a nuclear weapons expert. Hopefully one of those will chime in about the UK's nuclear depth
Defintely not an expert either.
I get most of my info from an U.S. navy sonar operator who has had a decorated career.
His Youtube Channel:
https://www.youtube.com/channel/UC9bMgCQyFNaMPsK9GtzM5dQ
Only someone who lives in a fantasy world would think that the Russians wouldn't suffer severe losses with major cities gone etc etc.
But yes, Russia has an incredible strategic depth and would certainly come out the winner in the nuke Department. Although in an all-out nuclear war, there would be no real winners.
Yeah, I agree, while Russia has a larger SSBN fleet and more nuclear weapons. Having an all out nuclear with any country with nukes is going to be devestating no matter who destroyed the other 'more'. Let alone that it would never stay between Russia and the U.K. at all... (USA, Nato,...)