Were these lies and not the truth?

The police investigated the No 10 parties for 6 months and issued fixed penalty notices to quite a lot of people, but most of those people were civil servants or advisers. Boris (and Sunak) were fined £50 for one "party" which was actually a meeting arranged in No 10 for a few people (who all worked together anyway). That breaks no rules. The problem was that Carrie gatecrashed the meeting with a cake (for Boris's birthday) and with her interior designer (Lulu Lyttle IIRC). The presence of Ms Lyttle made the meeting in breach of regulations. As it happened the cake was simply handed over and they left within minutes.

Fining Boris and Sunak for this is very questionable and they would have been well advised to challenge this - the CPS would almost certainly not have prosecuted. But - as Nadine Dorries says in her book - Boris was NOT well advised. Oliver (Olive) Dowden advised him to just pay the fine and apologise. But Dowden was among those trying to get rid of Boris. 

That's the only breach of rules that the police could find for Boris and, as Boris said, it was the biggest stitch up since the Bayeux tapestry. If you've watched the C4 "factual drama" Partygate you will have noticed that Boris appeared very briefly at "parties" (i.e. meetings) to say a few motivational words to staff or to thank a staff member who was leaving - and the people present were ALL people who worked together and it occurred in their place of work. So he broke no rules. Where rules were broken was after Boris had left and some went out to the local off-licence with a suitcase to get wine etc. This seemed to usually be the lovely Ophelia Lovibond in the C4 program (who played a special advisor).

However Starmer's "Beergate" party was an entirely different matter. This was not held in Starmer's place of work but at an arranged venue (Miners Hall) and a curry buffet was laid on for the 30 or so people who had been invited (who were not in a bubble) and it was not a work event. From film of the event people were wandering around drinking and carrying food from the buffet and not social distancing. And it went on for hours. The Labour party also tried to cover up who was there. This breaches so many Covid rules it's hard to go through them all - but most are obvious. Suffice it say that buffet meals are specifically proscribed in the regulations because of the dangers of cross infection.

The reason that Starmer got off is allegedly because the Durham police "don't prosecute people for historic crimes" - which is a bit odd since all crimes are historic by the time you've detected them. The only thing you got right Sid is that the difference between the two events is indeed colossal. Starmer drove a coach and horses through the Covid rules but denied breaking the rules, while Boris didn't break any rules but meekly paid a fine.