Not sure about a company being leased out, but I assume it is the same as if it was bought out. That means that the new owner is obliged to take on existing staff under your current agreement with your old boss.
If they wanted to get rid of you, they would need to make you redundant therefore you would be entitled to a redundancy payment. But, they cannot fill this position for 12 months (check on the liength of time). If they do, go for unfair dismissal! Also, try to keep an eye that some companies will fill your role with a different title. I know i got approached by one company in that situation and they just gave me a new title. I shoudl have heard alarm bells, but in the end they screwed me over!!
Think redundancy is 2 weeks per 4 & 2 weeks. So for 5 years you would get 12 weeks pay, tax free too.
Best of luck with it.