How strict is the U.K. border entry? [closed]

As I understand it:

The UK allows "Non-visa nationals" (including US passport holders) to be admitted for up to 6 months at a time for visitor purposes without a Visa. There is no formal rule explicitly limiting the number of visits or their cumulative length.

However there is a rule that visitors must not attempt to live in the UK through frequent or successive visits. There are also the general rules about not working illegally and having enough resources to support yourself and return home. The more time you spend in the UK the more suspicious the border guards are likely to be.

The general legal principle is that visitors entering the country is a privilege not a right. If the border guard suspects you are living in the UK, that you will work illegally, that you have insufficient resources to support yourself, or that you will violate the terms of your admission in some other way they can refuse to admit you.

I don't think anyone will be able to give you a quantitative figure for your chances of success. The statistics on admissions to the UK are simply not granular enough. Yes we know what proportion of US nationals arriving at the border are admitted but we don't know what proportion of US nationals trying to spend a lot of time in the UK and of a given economic status are admitted.

I would be especially wary if you are planning to travel to the same place as last time and/or if you have things that may tie you to the UK (for example a girlfriend there)

If you do decide to attempt this then you should gather as much evidence as possible that you are a legitimate visitor who can afford to make the trip without working in the UK and that you have ties to your home country that are strong enough to bring you back and yet flexible enough that you can afford to make long trips abroad.