You are extremely unlikely to get an ELCS and your tubes tied at the same time. I would be amazed if you do.
The general recommendations on sterilisation is to not perform it within twelve months of having a baby (unless of course there is a pressing medical reason to do so).
In part I believe this is to do with mental health and how pregnancy and hormones can have an effect but I also believe there may be physical reasons why this is not necessary recommended.
As I understand it, sterilisation when giving birth, really is pretty unheard of in this country nowadays.
If your primary or sole reason for the CS is the tube tying is the sterilisation, you are highly unlikely to get one.
If you want an ELCS for other reasons, then you might get one. However you CAN NOT insist on one. You have no 'right' to an ELCS no matter what anyone says or how much you quote NICE guidelines. You only have the 'right' for the most appropriate care for you circumstances.
I think you will struggle to make that case unless you focus on something in particular and form a strong counter argument to a VB.
Being overweight is not going to help you. Statistically, if you are obese you are more likely to end up with a CS (you just say you are overweight so I don't know whether you heavily overweight or just mildly overweight so I don't know how you fit in with this). However this is a result of being a higher risk in the first place and in these circumstances the risk of complication is much higher than in someone who is a normal weight. This is why doctors will try and avoid a CS in someone who is obese even though they are more likely to get one.
Having a hip problem, may not help you either. It would depend on what the source of your hip problem is - particularly if it is pregnancy related. Many consultants will try and avoid a CS in women with pregnancy related hip problems because surgery could hinder recovery and mobility further. Others will say that the risk of damage during a VB makes a CS better option. As I say, it will depend on what exactly is your problem and what the cause of it is.
I do not want to be the bringer of bad news - I am very pro-choice on the subject (having had one myself), but do recognise the need for women to be properly informed and for it to be done for the right reasons rather than on flawed or incorrect belief in order for both mother and baby to get the best care for their circumstances. You also need to be very aware of the hurdles you might face, and how you can tackle them as part of this process of making a decision with your consultant. The subject is highly politicised and very dependent on individual hospital policies. You need to be realistic in how you approach it. Simply 'demanding' a CS will usually get you nowhere as you do not demonstrate that you fully understand the implications. You have to demonstrate you are properly informed and understand the risks.
From your posts here, I would say you have a fair way to go before you get to that point. Do your homework, show you have really considered the alternatives and be reasonable in your approach and you'll have a much better chance of achieving what you want, though I do say that I really do think you need to adjust your expectations for sterilisation at the same time. I will be gobsmacked if you manage to get that as well and it could well undermine your argument for an ELCS.