Do I have a way out of this situation?

[GezHells]

There's one thing I'm still unsure about, before deciding on the way forward.

If I turn round and say, sorry guys, I'm out of here - is there anything they can legally do to force me to continue?

[silverlight1]

Ca you demonstrate that what you have delivered so far meets 60% of the "requirements".

If so I'd document this in writing to them.

[jmo21]

If I turn round and say, sorry guys, I'm out of here - is there anything they can legally do to force me to continue?

They cannot physically force you.

Whether they can sue you for breach of contract is a different matter.

[BlasterBates]

Sounds to me like the project is over, however if they get back to you I would try and finish it. No-one can force you to do anything, but that would have a good case to sue you if the project isn't finished. As you say they have paid. Only if they hadn't paid could you argue that they'd breached the contract.

[Willapp]

I used to fret a lot about these hypothetical situations. In reality the only way the client is going to take legal action is if the cost of such action is less than they stand to gain from forcing you to complete the work. In other words, how much is the remaining 40% worth and what does their business stand to gain from you finishing the work?

It would help if you had something in the contract regarding termination clauses, but in the absence of such clauses then assuming you can prove that you've done 60% of the work and that's what you've been paid for, it sounds to me like you can call it quits and not be too worried about any repercussions.