How can voters give her a mandate re; the Eu when we haven't got a clue what the details are? Are we supposed to just 'trust Theresa'?
The mandate required at the moment is to negotiate the exit from the EU and in so doing to get the best possible deal for the UK. To achieve that it is essential that the EU are facing off against a strong UK team, free to deploy any leverage/strengths that we have. Also that the EU do not have added leverage through seeing the UK continuously discomforted - even hamstrung - by a bunch of distractions at home, largely being undertaken to achieve the EU's preferred outcome of seeing the UK remain within the EU.
There will be no 'good deal' forthcoming if the EU have the luxury of seeing these machinations and can play to them. This especially includes the wrecking amendment that was attempted (dressed up as 'meaningful vote') and Hilary Benn's attempt to bring the same mechanism back through the Brexit Committee. All that would have done is to invite the EU to give us the worst possible deal with them having the sure knowledge that it would be rejected by a pro-EU Parliament and we would never be able (allowed) to leave.
Without this support the EU might just have to 'negotiate' and, instead of continuously laying out their Red Lines etc. have to start considering our positions.
This is little different than the way the EU have ensured that the 27 and all its governance functions are lined up four-square behind their negotiating team. Why is it UK citizens speak admiringly about the robustness of the EU position and lap up all their bold statements about just what we must and must not do, whilst at the same time are happy to rubbish and in some cases actively undermine, the UK's.
With regard your desire to have a look ta the details, there will be a number of opportunities. The PM has committed to give a vote on the final deal - and rightly this must be a take it or leave it vote. Given that we all know this will take years - if we do come out and you do not like it - then I am sure that either or both of the LibDems and Labour will be campaigning on a ticket to take us back into the EU and you can vote accordingly - that would be the vote on the deal - so you cannot claim that there will not be the opportunity.
You can be sure that the EU will leave the door open for re-entry in 2022, indeed having expected to win in 2016 and then throughout 2016 to 2017 though the actions of their sycophants, the EU who have been very good at playing the 'long-game' for decades, will most likely see 2022 as their final opportunity and plan accordingly. I can see them pushing to get some arrangements in place that secure our money until then whilst not giving materially on their core principles and then planning to offer 'time-bound opt outs' on all areas deemed key to the UK, e.g. immigration controls. This might see a resurgent Labour win on a re-joining, ticket or a LibLab pact supported by the EU promises. Of course the 'time-bound opt-outs' will expire and we will be back on the full integration journey.