Answer:  The other set MUST ALSO be 1 pound+50p+20p+10p+5p.
You didn't say the second set MUST be different from the
first.  :)

There is no other way. If you break any of those 5 coins
down into smaller denominations, there will always require more 
than 5 coins.  There are four ways to make 1.85 pound with 6
coins:

1.  (Three 50p)+20p+10p+5p 
2.  1 pound+(four 20p)+5p
3.  1 pound+50p+(three 10p)+5p
4.  1 pound+50p+20p+(three 5p)

but as you see, any way you break one of those 5 coins in
1 pound+50p+20p+10p+5p down, there will always be more
than 5 coins.  Therefore, the other set MUST ALSO be 
1 pound+50p+20p+10p+5p.

Edwin