Double Glazing Scam - Entu group

I don't know if it is the season for scams by unscrupulous DG salesfolk, but I am being inundated by cold calls, some of which mention the New Green Deal scheme - no such scheme exists. I admit I do need to replace at least 50% of my windows but shall choose a local, reliable firm that treats its customers with respect.
My experience in the last 8 days is as follows: After receiving cold calls about a window scrappage scheme (£2500 off replacement windows!!) I accepted an appointment for a rep to visit on Thursday 20 April at 12 noon. Sadly, no-one turned up. On Saturday a man rang (claiming to be the factory manager), he apologised that the rep never showed up on Thursday and that if he was permitted to come along in the evening he would give an extremely keen price for replacement windows. Appointment time was agreed for 5pm but once again this proved "no show"!
On Tuesday 25 April another cold call spiel resulting in an appointment by a rep for 4.30pm. This being the 3rd appointment... you'e guessed it another "no show". Today I received a phone call from a lady to apologise for the "no-show" - apparently the rep was in a "car accident". No-one had bothered to inform the customers. On asking how he was, I was informed he suffered whiplash... then, after a pause the lady happened to mention he was in hospital ...in traction. Oh dear! She then promised me a further 20% discount to make another appointment this time at 4.30pm. Its now after 5.30pm and… the fourth “no show”!! Unbelievably consistent! Can anyone beat this??!

I should point out the first paragraph the firm called itself "Weatherseal" and as regards the the second paragraph it called itself "St Andrews". Strange, as it cannot decided which name to call itself ? Just waiting for Penicuick to contact me next – after all, these companies are all the same – part of ENTU group. I reside in South Scotland and these companies have bases in central Scotland 80 miles away.
Best advice is to avoid any companies involved in the ENTU group (there are 10) ] as they are nothing but a crowd of sharks - instead use a local installer who will undoubtedly be more respectful and honest towards customers, as well as offering less inflated prices!