I am not sure I understand what Sender ID is suppose to do.

I thought it would appear to come from a certain number, but in testing it continues to show from +44 7800 000195 and putting any information in Sender ID seems to make no difference at all.

Only have 2 test messages left. Please advise what is the intent of Sender ID and/or what am I missing to appear to come from another phone number?

The sender's Id should appear as the SMS sender when received on a mobile phone.

Please note if you are sending the US (or any number starting with +1) then our system may force the Sender's Id to be a number.

If you want to change the sender's Id when sending to the US, please go to your account preferences, click on the International tab and uncheck 'Americas (1) - Force Compatible Sender's Id' and click 'Save Changes'