We're putting two large glass sliding doors into our new extension. Architect's drawing has the opening at 4960 x 2250. Friends have used ultra-slim line (aka fineline) aluminium frames which we like very much.

We'd appreciate some help please:

1. How much of a difference are the 'ultra-slim' frames to current 'standard' slim frames?

2. What sort of price should we expect to pay for the above sizes and who are the most reliable manufacturers/suppliers/fitters in this area of glazing? We live near Watford

Our friends suggested not to use the company they chose. It seems an area where suppliers ramp up the price but we appreciate the technical challenges etc.