It's very easy to get overexcited, and want to jump in straight away but it is a good time to stop and think.
Once you verbally accept or sign your contract things are set in stone, so it's very hard to start negotiating salary or any other logistical things that are important to you.
When you've had a job offer you are generally in quite a strong position, if the salary has not been previously discussed and agreed. Make sure that you'll be happy to have a range of salary as opposed to a set number. This allows for a bit more flexibility from the employer. Remember that you are asking for a possibility of the change in salary, not demanding one.
The bottom line is that you need to provide a strong reason as to why you're worth more money.
If you are working for a London company, it's likely that the salary will be higher. This contrasts to a company that is based outside of London (where the cost of living is generally lower).
If you're taking a fully remote job the salary may be less, but bear in mind you're likely to save a lot of money from not having to commute. You will also be saving time and effort from being able to work pretty much anywhere.
Whenever possible its better to have the conversation on the phone or zoom - its easier more professional and things are less likely to be misinterpreted.
It’s a good idea to prepare for this with a script of what you might say and practising it beforehand in the mirror or with someone else, and role-play the situation:
Hello, how are you? I just wanted to say thank you for your recent offer. Before I accept, I was wondering if it would be possible to talk about salary? Due to (X reason) I was wondering what the possibility of raising the salary would be from the companies’ perspective?
…And go from there.
https://hbr.org/2014/04/15-rules-for-negotiating-a-job-offer
https://www.vestpod.com/news/2020/7/7/how-to-ask-for-more-and-not-feel-guilty-about-it