This is my experience buying a house in London.
Freehold vs leasehold
First thing to know is that there's Freehold, and Leasehold. Flats are almost always Leasehold. Leasehold is kind of like buying a flat in Sweden, except that the house is controlled by a faceless corporation that charges whatever service charges they feel like, have a bunch of restrictions, and no real incentive to do a good job.
You'll get a knock on the door from some guy saying he's there to change the smoke detectors, or inspect the pipes, or whatever.
Every Leasehold property has a Freeholder who does not care about you, who is the one who really owns the place.
My experience in Sweden is with renting and owning a flat in a BRF that encompassed just that building, so it was owned and managed by the people who actually live in the building.
You could put it like this: There are three parties involved in owning a flat:
1. You. You paid a lot of money to have exclusive right to your flat, be allowed to drill in walls and do all kinds of things inside your flat that a rental would not allow.
2. The owner of the building.
3. The people who manage the building.
In Sweden (2) is you and your neighbours. This means that for small houses (3) is often also you and your neighbours. Your voice is heard, and you get to vote about who actually manages the building.
For Leaseholds in the UK (2) is "The Freeholder". You rent your right to have your Leasehold. It costs a few thousand to renew that lease for a couple of decades. It's normally kept at around 100 years, but if it goes down below 80 it starts getting really expensive, and you may not be able to get a mortgage. And people won't want to buy it, so this could screw your investment.
Since the Freeholder isn't the collection of Leaseholders or inhabitants, and the Freeholders decide how the building is managed, the only selection criteria for building management is "as cheap as possible for the Freeholder", with no consideration at all for the Leaseholders.
So in short: get a Freehold if you can.
Solicitor
In Sweden the only third party in buying a house is the estate agent. In the UK aside from the estate agent both you and the seller have a solicitor. All communication between buyer and seller goes via these lawyers.
You probably have to chase the solicitor, to make sure they actually do what they're supposed to do. E.g. when I contacted the solicitor asking if some final paperwork is done (after waiting weeks), then coincidentally it "just" arrived, and they'll send it via post today. This is apparently normal, and one cannot just wait and assume the job will be done.
We had to change solicitor. We originally chose the one recommended by the estate agent, but turns out they were not registered in the system for our chosen mortgage provider. And they would not be able to register, either. So we had to switch.
Our first solicitor had a different issue, too. Because of covid this was all done over the phone, email, and post. We were going to send a copy of basically all our IDs and financial information, so we wanted to check up on the lawyer. But we couldn't find them on the SRA website. SRA is where all solicitors are registered. The phone number and company of a person with the name of our solicitor did not match. Turned out to be a screwup at the SRA (Solicitor's Regulatory Authority).
How bidding works
In Sweden everything is an auction, and you can see the highest bid. The UK has auctions, but most are listed for a price. based on that price you can put in an offer, that's higher or lower. That bid is then accepted or not.