They shouldn't bend to the will of their constituents if they believe it's not in the best interests of the country. Why do people think being an MP begins and ends with their constituents? The order is: Country Constituents Party That's it. So if an MP thinks their constituents are wrong and what they are asking is not in the UKs best interests then they should have the spine to go against them.
The numbers are more nuanced than that. I don’t know the Barnsley totals; but roughly 1/3 of Labour voters voted for Brexit. If we assume that ‘most’ of them will vote for an ‘out’ party, though not all as Labour isn’t an ‘in’ party, they’re offering Brexiteers another roll of the dice. So maybe 4000 Labour voters will vote for a Brexit party, if no Tory voters move to the Brexit party, then Labour win, if all the Tory voters move to a Brexit party, and they pick up some more Labour votes, they’ve a small chance of a win. You have to play this out in more marginal seats to see the Brexit party scooping up seats. In really safe Labour seats like Barnsley it wouldn’t matter, the Brexit vote will be split between 3 parties (4 if you include people who voted for Brexit and will still vote Labour).
it not all ******. ask yourself who is going to do the best for you and your family. ask yourself who is going to do the best for the area you live in. ask yourself who in the next 10 to 50 years of your life is going to make the best of whatever is the fall out of brexit in areas that matter to you. if the brexit issue is clouding your judgement id just say look beyond it.