Thanks for your post to add more clearance as we get nearer to time 
So I entered data into both calculators and results match spot on at default 50%
However,
Changing the TARGET MARGIN figure, the results do not match and below are the actual results I got on 2 entry examples:
ACCOUNT VALUE: 59370
BLOCKED FUNDS: 24182
On Richard.W calculator-
TARGET MARGIN: 49.5% gives result of- £480.45
TARGET MARGIN: 49.3% gives result of- £238.63
On obrienciaran calculator-
TARGET MARGIN: 49.5% shows result of- £0
TARGET MARGIN: 49.3% still shows result of- £0
In fact, it shows £0 result from 49.4% and below. 49.6% shows £601.36- It seem to skip the 49.5% when trying to move, it jumps from 49.6 straight to 49.4 and I have tried a very fine move/adjustment.
I hope it doesn’t add more to the confusion and Thanks again!