If you do an internet search for your NHS area and "weight management" you should be able to find out what services are on offer in your area.
In my area, there are programmes you can sign up to directly that are lifestyle related, eg a digital coaching app, access to "wellbeing" advisors who offer tailored advice, support and motivational interviewing.
Then if that isn't suitable they also offer an NHS Digital Weight Management Programme which is a 12-week online behavioural and lifestyle programme, but to access that you need a BMI of over 30 and either diabetes and/or high BP.
If your BMI is over 40 then you can ask your GP to refer you to the "Tier 3" weight management service, which may mean access to a dietician and perhaps eventually being offered bariatric surgery. There will be waiting lists for the referral and then for any treatment.
It depends on your NHS trust as to what they offer, so you need to find out about yours. As you can see, your GP is likely going to tell you about the first level of assistance, so apps, wellbeing advisors, or similar.
What your GP is definitely not going to do is to prescribe you Mounjaro, or any other prescription medication for weight loss.