Felt roofing is still widely used but has the shortest life and is prone to leaking and deterioration due to the varied weather in the UK.
People still insist on replacing felt with felt due to the lack of knowledge of other materials this is what gives flat roofs such a bad reputation.
If you are replacing a felt roof please consider using EPDM rubber or Fibreglass GRP these are top products with long Guarantee's and very neat looks.
Please take time to look at these on are services page.