Firstly...for Jersey being turned into a 'Watford' clone, have you looked at Fitness First, AquaSplash, CineWorld and the complex around there lately? The conversion of Jersey into an unsightly part of the Home Counties is already happening! (Reminds me more of Stevenage personally).
And, secondly, we've already had large chains from the UK move over here and seen the consequences... HMV came and Seedee John closed up his town shop to concentrate on his business at the Powerhouse and the Music and Video Exchange closed (and, incidentally, HMV were initially able to undercut other retailers but took advantage of the introduction of GST to raise their prices to UK ones adding an extra 17% throughout the store), WH Smiths took over the Lexicon and were followed over here by Ottakars (now Waterstones) and so the Jura bookshop closed both its branches, the Printed Word shut down and the bookshop in de Gruchy, having been taken over by Waterstones, is now closed - now there are only two places in Jersey to find a decent range of books and they are both UK multiples...and, yet, the States did nothing about these examples so why should the introduction of a UK supermarket chain justify such delay and consideration...it may be lamentable, it may be unpleasant but this is the way of the market, the way of the world, the law of the business jungle...if a shop is offering consistently what the customer wants, high quality items at a good price combined with a good level of customer service and is agile and able to react to demand, knowing what the customers want in the local marketplace and offering it to them, then it should have little to fear from competition - in fact, the competition should act as an incentive towards higher standards. The current situation over here is all too often one of lousy customer service, the most obvious items being consistently out-of-stock or unobtainable and ridiculous over-charging because they think they can (The worst example I have come accross was two shops opposite each other with a price difference of £1 on identical bottles of spring water - £1.48 in one and 48p in the other!). In fact, with very few exceptions, the poor level of retail service over here seems only to be justified by the fact that these shops can get away with it, with employing staff to whom serving customers is secondary to discussing their activities the previous evening, with failing to carry consistently in stock the most obvious and everyday items, with charging whatever they feel they can get away with, and customers let them continue doing it because they can't get to a hypermarket offering decent prices to shop every day, because these are goods they can't buy online or simply because the customers don't know, don't expect or have never experienced any better. Open the doors wide and invite over Aldi and Lidl (and let's have Primark over here as well) and, ok, some local shops will go to the wall but, as I already said, that's happened before when UK retailers have been allowed in - the shops that fail will be the ones who do not react, who do not concentrate on offering a core service and doing it very well, who do not develop a unique selling point to differentiate themselves from the competition and, quite frankly, they will deserve to fail - it's a tough world out there. With competition there will be an incentive for local retailers to try harder in all areas of their business and the result would be positive for customers islandwide. By maintaining restrictions on supermarkets over here the local customer is condemmed to continuing high prices and low standards in the retail industry.
(And what is going to happen with the old Abbattoir site? Conventional retail logic has it that any developement of a mall or shopping centre has at least one and preferably two large flagship stores from large multiples to anchor it and ensure footfall. Will this not happen for fear of introducing undue competition in the local market?)