TUPE is quite complex, even for small employers, but there is no reason why you should lose out over this. From your second post, it seems that your original employer does think it has transferred your employment undertaking to the second, or it wouldn't be thinking that holiday rights have transferred.
As well as the links provided by others above, you might wish to read this
http://www.acas.org.uk/TUPE
and download the leaflet published by ACAS on it.
You should also contact ACAS for advice in your situation.
At he very least your original employer should have consulted with you on what was on offer, and confirmed what the arrangement was supposed to be in writing.
If he has dismissed you through redundancy, he should have given you notice (probably five weeks in your case, and certainly not less than 5), then either asked you work the notice or pay you money in lieu of. Also he should have paid your holiday to the date of dismissal, AND redundancy of at least the minimum statutory amount.
If he thinks he has TUPE transferred you, he should have confirmed that in writing to you. Neither of these things seem to have happened.
It is beyond the scope in a few words to explain whether TUPE applies or not - ACAS can and will help you with that. It is in essence driven by the nature of the relationship between what is closing with the first employer and what if anything of it the second employer is taking over.