Thank you for your reply dx100uk.
The letter says
" We must ask you to pay the sum of £xxxxxx direct to this office,
failing which we have strict instructions to issue a Count Court Summons for the full balance plus fees and costs.
We are instructed to seek a judgement against you which will be registered by the court, if obtained"
it goes onto say that their client (global arrow) is willing to accept payment by instalments
and can offer a specially discounted rate.
The default does appear on my file.