Jonathan is performing in September in London

... in St. Paul's Church (Covent Garden) on 22 and 23 September at 8 pm.
In production called "A Shakespearean Handan Dream".
It sounds really interesting.

Jonathan was also mentioned in today's EveningStandard:
http://www.standard.co.uk/news/londoners-diary/londoners-diary-tory-mps-may-lose-their-seats-too-a3334416.html
...But another Firth has an opening too. Jonathan, Colin's younger brother, will be appearing at Covent Garden's St Paul's Church, also known as The Actors' Church, in The Shakespearean Handan Dream, which marks the 400th anniversary of the death of both the bard and Chinese playwright Tang Zianzu, by presenting a work that draws from both.
We do hope Colin doesn't mind a bit of fraternal competition...

http://www.wegottickets.com/event/373357

William Shakespeare and Tang Xianzu works are united in an East meets West celebration marking the 400th anniversary year of the internationally famous writers’ deaths, staged by collaborating British and Chinese practitioners and performers as Ke Jun and Leon Rubin realise their 6 year collaboration The Handan Dream.

Shakespearean characters such as King Lear and Macbeth enter the world of Lu Sheng’s existential dream, expertly delivered by a mixed cast of Chinese and British performers including Jonathan Firth. 
The Handan Dream is the final of Tang Xianzu’s famous four masterpieces. In the original text frustrated scholar-official Lu Sheng meets an immortal at an inn, to whom he complains to about his lack of success in the imperial exams. In order to enlighten him, the immortal sends Lu into a dream of a whole lifetime, a fifty-year political career of successes and glories, excesses and failures. Upon waking Lu then discovers he is still in the inn no time has passed. A statement on the transience of human existence and futility of earthly desire and ambition. Having seen and tasted for himself the heights of luxury and privilege, Lu Sheng sees that they all eventually lead ultimately to suffering and disappointment.

In this adaption, events in Lu Sheng’s dream are echoed by the characters, themes, plots and lyrics of Shakespeare’s plays, creating a dialogue in which the questions of ambition and desire are treated according to the contrasting attitudes and cultures of Elizabethan England and Ming China.