I'm not really sure why being in the UK would make any difference. The price is in dollars whether you're a DVCer in the UK, US, or anywhere else. Yes, we have exchange rate fluctuations to contend with, but without the dining plan, if you're eating on Disney property, you will still be buying your food in US dollars regardless. Therefore, the argument for whether the plan makes sense or not doesn't really change. Even if the exchange rate is excellent, it doesn't change the calculation, because this reduces the GBP cost whether you get the dining plan or not. So the argument that its hard to justify for
UK DVCers doesn't make any sense.
The plan can definitely make sense depending on your dining preferences. For example, one of the main attractions of Disney for us is the dining (and the food and wine festival). We typically do a three week/21 night vacation. We get the Deluxe dining plan which allows us to dine at a different signature restaurant every night of the week and live like kings. We do one whole week at the Food and Wine festival (usually in the second week of our vacation) and we don't pay a penny there, since between the two of us we have 84 snack credits. There is something nice about being able to completely ignore the price column on the menu. For us it works well because of the type of dining we like to do, and the type of food we would
normally order. We don't feel compelled to order the most expensive thing on the menu to "maximise" the value of the dining plan. We're pretty confident,
at worse we will break even because of what we normally eat. Is it too much food? Actually, if you do a signature each night, the portions in the signatures are fairly 'normal' (i.e. not huge mountains of food), this uses up two out of your three dining credits per day, meaning you can have a medium/large breakfast, and then a nice three course meal in the evening.
It all depends on what you want to do. If you're not massively in to the signature dining options and the food isn't a big part of your holiday, then no, it probably doesn't make sense - but that's not because you're a UK DVCer