so, say the original price is "x" pounds, namely the 100%, then it gets increased by 12% and lands on £190.40, so £190.40 is really 100% + 12% or the 112% then.
since we know that £190.40 is 112%, what is "x"?
[tex]\bf \begin{array}{ccll}
amount&\%\\
\text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\
190.40&112\\
x&100
\end{array}\implies \cfrac{190.40}{x}=\cfrac{112}{100}\implies \cfrac{190.40\cdot 100}{112}=x[/tex]