Today a citroen garage regassed my air con on my picasso and spilt what l think is air conditioning treatment all over the dashboard and central console. The car stinks of chemicals, are theseharmful to breathe in and how do l get rid of the smell. Citroen have been of little help.

The refrigerant inlet & outlet valves should be under the bonnet & r connected by airtight connections to a sealed machine which changes ur refrigerant, therefore l would think that the smell is not refrigerent (ammonia smell), unless ur heat exchanger is leaking (why did u need it regassing)?
If so take it back to the shop for diagnosis ASAP as at best u may damage ur AC compressor & at worst u may be made quite ill by the fumes in such an enclosed space. Drive with ur window down until u get there.
Often, corrosion pinholes in the pipework do not become apparent / leak, until the system is repressurised.