I'd check the legality of what your supplier is doing though Paul as it's illegal to sell or barter a great crested newt or any part of it (could include eggs?). Here's a link to Froglife & you can open a page about 'Legal Protection'. You're not allowed to disturb them in the wild without a licence & this has led to lots of delays in building works as the sites have to be inspected (& can only be inspected at certain times in the year so as not to disturb breeding etc.) & licences granted for them to be rehomed etc. Apparently we have quite a lot in the North West & especially in Cheshire where people are always wanted to build large expensive homes to live in & being held up for months by newts!
I saw some great crested newts at a garden centre about a month ago, the guy had brought them in from his own pond to show people & he had a licence & had written a book about them, they were bigger than I thought & very 'prehistoric looking!
Froglife - protecting amphibians and reptiles in the wild