Homes are valued usually by a £/ft² formula so if you are not reducing the actual size of the property the theory is that the price should stay the same, however in practice you will find with homes of the same size the 3 beds will sell for more than the 2 beds.
The actually amount they differ depends on the area you are located and the local market values. In my area where I live for example say the average home is valued around £100,000. I would say the rule of thumb would be there is going to be circa a £15k difference between 2 and 3 beds of the same size.
If you are just after trying to get a bath in your home, the renovation work is probably not going to be worth it in the long run if you are looking to lose a bedroom. It sounds like overkill to me, I haven't of course seen your property but generally, this extreme renovation is probably not required; most of the time adding a bath is quite possible with the current layout using a bit of creative design.
Measure up your current layout and have a play with some free house design CAD like Sweet Home 3D.
I'm not a fan of these books and videos from people selling "wealth through property", they all generally say the same thing with varying degrees of useless filler and penned by someone with insignificant experience in property but is great at selling courses.
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Rent 2 Rent is hardly a difficult method to master and adopt:
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That's the R2R basics summed up in 7 bullet points instead of a 134 page book. Written by myself who has a relevant degree: BSc Estate Management, Valuation and Law, not someone who's property credentials expands little further than "they live in a house" . I've just checked, Samuel Leeds' book is £10.99 on amazon, I will do you a deal and only charge you £5.
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I would suggest your time would be better spent reading up on the actual law and legislation surrounding property. My suggestion would be something like: https://www.amazon.co.uk/gp/product/1905391854/