Ph.D. Topic Problem- Changing Topics/Labs Even though title itself seems quite similar to other questions asked here, my question is a bit different from other similar questions. I know it's a bit long, but I do appreciate anyone who has a read through it. 

I am a Ph.D. student in UK and it has been 5 months since I started. My topic was something completely new (to me) so as one might guess, I've spent these 5 months reviewing the literature and covering what I didn't know. Problems started right here.

I am working at a Research Institute that has expertise on something totally different than my Ph.D. (let's name it field A, and name my Ph.D. field B). Simply, A and B have nothing in common (except both are engineering topics, but sub-fields are different). As a result, this laboratory doesn't have the required equipment or facilities that I need for my Ph.D. most importantly, there is not a single person around me in the lab who has a single bit of knowledge about my topic, thus no practical help or chances of hands on experience. Speaking of the good parts; I am getting a proper work experience (since this research institute has industrial focus), my scholarship is a substantial amount and my supervisor (even though he is sort of clueless about my topic, he is a huge figure in field A) is quite impressed with my progress.

But, as always, I have an alternative. There is another lab in my university which has expertise on field B (my Ph.D.). In this lab, there are people who have expertise in field B and of course, director of the lab is a powerful figure in field B. I know it sounds good so far, but here are the cons of this alternative: Lab director  can't give any sort of guarantees regarding a scholarship (which means I have to pay tuition fees as well, good old UK) and  wants me to work in a new project(a new field, field C). This field C, again completely different from A and B, is a newer topic compared to B and there are lots of research going on in this field. Field B is sort of an established field, I am just trying to squeeze whatever's left out it.

So on one side, I have a good working experience, Ph.D. in field B, an impressed supervisor, yet no practical help about field B or collaboration whatsoever. On the other side, I have a group of people who have expertise in field B and C, yet no money. I personally don't have any problems about changing my Ph.D. from B to C, the only disadvantage will be losing 6 months of work and naturally, getting 6 months of extension in the end. On the plus side, I already have a paper waiting to be published (in field A though, not in my Ph.D. topic field B). Therefore, these 6 months won't be "that" lost.

So, both sides are waiting to hear from me as soon as possible. I have to make a decision by this Friday. Last thing that should be mentioned is my current lab is located in city 1, whereas the other one is located in city 2. I hate city 1 (current city), whereas I am in love with city 2.

Financially, I am promised by the other professor that depending on my performance, I can get funding. I do know I can't trust this, though I believe I can cover my expenses throughout my Ph.D. including tuition fees. So, money is not a big problem right now.

If I go to the other lab, field C will be my Ph.D. as well as my work, hence shielding me from dividing into two as I do right now for field A and B.

My question is simple, what would you do if you were me? I have exhausted my friends and my family about this issue and I need a fresh pair of eyes and neurons to help me out.  I do appreciate any questions and comments.
Whichever makes you a happier person. Life is short and not worth spending 5 years in a condition you don't like. If you have the money, go for it. If not, here is my longer answer.

The work experience you are getting in field A should not be a priority because you are there to do research, to contribute to science. Work experience in that field should be just a tool so that you can earn money and live properly. The excellency of people in field A are also irrelevant, as your research is in field B.

But, life does not always present us the best options. If you cannot get a scholarship when you switch to field B, then I would definitely stay at where you are now. You say you can cover expenses, but if you don't get a scholarship, how much will you lose in 5 years? That's a big number and imo not worth it (unless you have a million in some account)

I would stay there and from time to time, consult professors that work in field B. After some time, as you dig deeper, you will know more than those guys anyway.

It really depends on your budget I guess. I am not rich so I don't like the idea of Ph.D. level scientists' paying for it.