Unidentified crustose lichen

Unidentified crustose lichen

Observation - Unidentified crustose lichen - UK and Ireland. Description: Grey crustose lichen, in circle formations from 1cm to 2 in diameter, on upward facing cement substrate in suburban location. Seems very common so I'm sure someone with some lichen knowledge will easily be able to help me identify this, however the phot

Grey crustose lichen, in circle formations from 1cm to 2" in diameter, on upward facing cement substrate in suburban location. Seems very common so I'm sure someone with some lichen knowledge will easily be able to help me identify this, however the photos on www.britishlichens.co.uk and too magnified compared to mine to enable me to compare.