Solenopsora candicans or Rhizocarpon umbilicatum

 Last Saturday we found the following lichen on a limestone rock near Kettlewell  

Recorded it as Solenopsora candicans. However now I wonder if it was really Rhizocarpon umbilicatum?

Can anyone give advice? This is the specimen

It had a thick white thallus.. and I can see a mollusc had been enjoying it..

Unfortunately we did not test it with chemicals

Dobson says R umbilicatum is C -, K+ yellow

S. candicans: K- P+ orange and presumably C-

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The next day I was at a limestone wall above at 350m near Leck Beck, Lancashire (almost Yorks and almost Cumbria) and I found this lichen which I thought was R umbilicatum and tested it with K. After about 5 min it went this mangey yellow  (and nothing with C)

Rhizocaropon umbilicatum Wall between Leck Beck and Leck Fell House

Rhizocaropon umbilicatum Wall between Leck Beck and Leck Fell House

Rhizocaropon umbilicatum Wall between Leck Beck and Leck Fell House

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Here are some pics I have taken in other places when I have been sure it was S candicans in the past. These all have a distinctily placodioid thallus (-thallus with pleated edge) 

Solenopsora candicans

Solenopsora candicans Ingleton

 Solenopsora candicansIngleton

Solenopsora candicans - Winskill Stones

Solenopsora candicans High Hill Settle

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Rhizocarpon umbilicatum

R umbilicatum Highfolds with Allan Pentecost

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Earlier we had found this pale yellow Caloplaca on the church wall at Kettlewell. Because of its colour I said "Caloplaca limonia".

But looking at pictures on the internet all the internet pictures I am not so sure.

Possible C limonia   ??