Agree with Butchersapron that aside from what groups like Solidarity & Big Flame produced at the time there's not one book that goes into the limitations of Bennite Leftism in that period. What Sihhi's done is a lot more relevant to Bennism as policy than what I've done which is all about where labour militancy in that period came from.
If you want a critique of AES/Bennism as policy and why it failed, then a good place to start is the literature around the 1976 default and why Benn lost. Kevin Hickson's book isn't radical, but it explains in pretty practical terms why at that top-table level it didn't work.
If what you're looking for is not why it lost, but why it would have been a total shambles for workers if it had won, you want to be looking at the forms of "worker participation" that were actually implemented with Benn's (direct) support. Both at British Leyland and Chrysler UK participation not only did the schemes fail but whilst in force they actually further disenfranchised workers and exaggerated existing tendencies toward bureaucratization, and for a variety of reasons the majority of workers at both companies hated them.
For a general sense of why this was the case you need to go back to the 1960s. Basically, in the mid-1960s manufacturing employers get a sense that the post-war boom has come to an end and they're about to enter a phase of intense competition (initially over exports, later imports) and they urgently need more capital investment, rationalization and higher productivity. Co-opting shop bargaining is a big part of this plan, Ford is involving its employees in re-grading schemes in 1967 and lots of other employers are moving toward "productivity bargaining" where you swap pay rises for co-operation on productivity (and of course speed-up, redundancy etc etc.). Long before the political left-wing of capital comes along and start suggesting planning agreements and all the rest, advanced sections of capital are trying to do this for themselves. (dare I say it, Tony Cliff's The Employers Offensive is good on this, especially if you focus on his analysis and not his solutions, there's a reason why the IS sold so many copies to shop stewards and convenors).
Fast forward a bit to workers participation and you've got Benn's schemes at British Leyland from 1975 that followed exactly this logic - industrial democracy as a means of improving profitability - and the result is entirely predictable. Senior stewards got dragged into planning meetings where they helped management raise productivity and agreed to flexible working for the good of the company (because that was the logic of participation...), things they later pretended to oppose in negotiations. I've got some academic report on the planning agreements for the Mini Metro, where Derek Robinson et al. agreed to all sorts of noxious shit in the planning stages - I'll dig out the reference tomorrow - like massive reductions in labour load, new machinery, flexible working etc. More than that you've got key union personnel discussing how to make everyone work harder 12-13 days a month instead of in the factory supporting people. Finally, you've got the problem that most workers weren't interested in managing their own exploitation, particularly when they'd already got substantial control over their pay and conditions. Why the fuck would you want to help run a car factory for the same wages that you got for fitting windscreens? And why would you want your steward sat in the office discussing how much more efficient you could be, rather than next to you standing up for your rights?
So basically exactly what anyone sane would expect to happen under co/self-management where the purpose the planning agreements is for the company to make a profit:
(most thorough treatment of the topic currently in existence is an edited vol. of mixed quality - British Trade Unions and Industrial Politics 1964-79, also prob worth looking at stuff for the Meriden Motorcycle Company workers co-op, although I've not looked at it myself)
). This was dirctly tied to their understanding of a crisis free bureaucratic capitalism, one in which organisation was all that really mattered - an idea which died a hard death in the early 70s. Useful idea but only in limited conditions.
