Sell or rent out? Need advice

sturgeon

It's early days but as my circumstances have changed over the last 3-4 years I was looking to sell my flat to move slightly closer to London, and get somewhere a little bigger. I live in the outskirts of London currently (zone 4). I've been obsessed with the idea of owning/selling as to me, moving back to rental just means I'm paying inflated prices and paying off someone else's mortgage. One of my friends recently keeps bugging me to explore renting my flat, rather than selling, then moving much more centrally and renting myself.

Initially, it seems after using some online calculators that I may be able to make a small profit of £400 monthly by renting my flat out, after tax/deductions etc. Dubious of this based on online calculators so I'll need to do the maths properly. I do know I have a wedge of equity in my property and bought for a good price, so expected there to be a decent gap between my mortgage payment and any income should I rent (the rental value is about £500 more than my current mortgage, although I know I'd need to change to a buy to let mortgage and inevitably my interest rate will increase, no idea how much).

I'm actually struggling with the pros and cons, I see it as follows:

Pro-The flexibility of rental and yes, I could choose a lovely flat in Zone 2, closer to work, more convenience around me and I'd choose a development with many facilities. However, my outgoing would easily be £500 more monthly vs my current mortgage payments living here, and that's incorporating the hypothetical £400 profit I'd make monthly from my existing property being rented. So the pro is only convenience and saving time.
Pro-Not selling and buying would mean I don't have to lose a chunk of my savings on stamp duty just yet. Although inevitably I will when I do choose to buy again so isn't this just putting it off?
Pro-benefitting from my existing mortgage being paid off thanks to the rental income and me building up more equity.

Con-Making do with being a landlord. I don't imagine this will be too problematic as my flat is a new build and very low maintenance.
Con-The fact I'm paying inflated rental costs if I rent out my flat and then rent my own. That extra £500 is actually about what I'm expecting my monthly mortgage fee to increase by if I sell and then buy the kind of property I want, and at least that is helping to pay off capital.
Con-the negatives of rental-it's not really my property and I can't turn it into 'mine' through decoration and installations with ease.

Any thoughts and anything else I'm missing? I'm not seeing the bigger picture or any overwhelming positives here. It gives me an opportunity to rent in a better area, development and location that I can afford to buy at it even if I did sell and buy, I can afford it but it's still coming at a bigger cost than my current outgoings. I am obsessed with having a stake in a property hence the normal idea of selling mine and buying another, however I guess I will still have that benefit as I'd still own my flat and be building up equity with the mortgage payments thanks to my rental income?