Using & to connect cells without changing value format

Hi,

So I am working on a report where I am connecting results into simple sentences.
I tend to do this using various 'if' functions along with some calculations.

However where I run into problems is in the formatting of values in this.
I am looking to keep values indicated by the thousand, but when I put into an & it breaks up the format.

E.g.

Current Mo 228,512
Prior Mo 252,608
difference 24
Total NFI has decreased vs prior month by

Total NFI has decreased vs prior month by 24096.0400000003k

What I am looking for is the final wording to be as below

Total NFI has decreased vs prior month by 24k


Formulas indicated below.
Current Mo 228511.78
Prior Mo 252607.82
difference =ABS(O19-O20)
=IF(O20-O19>500,"Total NFI has decreased vs prior month by ",IF(O19-O20>500,"Total NFI has increased vs prior month by ","Total NFI is in line with prior month"))

I have formatted the cells to show values as 000's but it reverts back when & is used.

Any thoughts on how to fix this?
Happy to work with other formulas as well.

Thanks,