Thanks for all your comments and advice. Yes, I will be giving them dormancy this year; I think I feel confident enough and will acquire a small wine-chiller just for this purpose. I will, of course, be keeping some plants out of dormancy - in case I lose them all - so they can serve the purpose of seeing if VFTs can survive for long if grown like this.
I have to clarify that some plants may actually have only missed 2, as opposed to 3, dormancies. The reason for this is that some are actually cuttings/splits of the main plants. I suppose if it's a cutting, the dormancy starts from 0 again? But I am a bit more curious about the splits - are these to be regarded as being part of the parent plant so that they can be said to have/have not experienced the same number of dormancies? In some cases, the "splits" are smaller than the parent plant, leading me to think that they are actually fresh, though unintended, cuttings.