Your question is very personal and nobody here can answer it except you. Buy bike you like or replace motor you have. Your choice, not ours.
I would recommend step through and TSDZ8 or TSDZ2B from Woosh. Both are more powerful than they look.
There are many Carrera and Cube Katmandu bikes, so...
Can you post a link to Carrera TDZ? Or you meant Carrera with TSDZ2 motor?
Shame you didn't ask before buying. Woosh has more powerful motors for sale than BBS01
You didn't answer the question. Do you pedal?
I think extra battery is the solution you are looking for. I have seen a nice rack to carry two spare batteries somewhere, but I can't find it now.
Polygon Heist X5 £399
You won't find them online. Look in stores Blacks/Millets/Go Outdoors
https://www.millets.co.uk/16562035/polygon-heist-x5-urban-bike-16562035
https://www.polygonbikes.com/heist-x5/
Heist X2 was £299
Just to be clear - cheap bikes are what they are. Cheap and low quality.
I don't see why person who is passionate about cycling would buy a cheap bike. The trick is to buy an expensive bike cheap.
BTW... what is a cheap bike? £100? £500? £1000?
Cheap bikes are usually bought by people who have no knowledge about maintenance. There is no surprise some bikes fall apart shortly after purchase as they are not checked properly after unboxing.