Hello all.
Firstly, thank you everybody who responded to this thread so far, handling a situation like this is made so much easier when there are people to offer you such helpful advice.
I have been in touch with Lindens who have confirmed the island is offline and have let me back in to collect my stuff...what a relief!
The owner of the land and his team are refusing to acknowledge any of my messages and so I have opened a dispute case at Paypal, who have been really helpful so far as have my credit card company.
So, I am very glad to have got my stuff back, even if my marketplace shop is offline and I am out of pocket.