Personal loan started before contract completed

NWHLondon

In November 2020 I entered a contract for some new windows with one of the nationally recognised brands (regrets, I have a lot).
Due to the Covid crisis, I decided to pay the entire value of the contract on finance, primarily due to the significantly lower deposit requirement. 
The finance was arranged by the company from whom I am purchasing the windows, but of course with a reputable loan provider. 
Since I placed the order, the window company have split delivery of the order in to two lots. 
Last week, the first lot of windows were fitted, however, the second lot will not be fitted until the end of March at the earliest. 
To my surprise, the window company requested payment from the loan provider for the whole value of the contract, which they have received. The payment was not meant to until the entire order had been completed to my satisfaction. 
As a result, the loan provider is now asking for payments in relation to the loan, despite the fact that the order has not been completed. 
Can anyone advise how I can resolve this as neither the loan provider or the window company are taking this issue seriously.
Thanks.

[Deleted User]

What do the terms say? It's unusual for payment to be delayed until completion of the work.

Edi81

Are you sure the loan is connected to the installation of the windows? I recall seeing someone on here who had been “sold” finance by the installer but it was just a personal loan from Tesco Bank. 

There’s not many companies that operate in this area - who is the loan with?