Predictions of Muslims "taking over" Britain are far off the mark - they make up something like 4 - 4.5% of the UK population and even with their more rapid population growth are in no way going to be anywhere near a majority. France, Germany, Netherlands, Belgium etc all have much higher Muslim populations that we do.
There will be more problems with integration and community relations if we try to discriminate against minority groups - it will build resentment and division. Worship and attending the Mosque is a very important part of many Muslims lives - and as someone pointed out much more important than Church to the majority of self-labelled Christians who don't believe in any of the real tenets of Christianity.
Thats not to say we need to encourage integration more - America has done it successfully although its Muslim population is smaller again, proportionally, and from much more affluent backgrounds in the 'motherland'. But you don't integrate by discriminating. You integrate by ensuring children are taught together, everyone has access to English language teaching, ensuring rules are applied commonly across groups etc.
I think if the Mosque gets built, it would be great, giving a focal point for what seems a disperate community in the city. But its likely going to look nothing like this 'concept' - it will be on a rain-sodden street and will be much less tall and graceful. Their fundraising quoted an amount of £5 million. Theres no way they could build THAT for such a comparatively small sum.