Is this correct?

Following problems with email bounces, my domain hosting company, Heart,
suggested I publish an SPF record for my domain fojd.org.uk and using the
wizard at www.openspf.org I published v=spf1 mx ~all

I still get a lot of bounces, particularly from Hotmail and ATT addresses,
and Heart have now directed me to a wizard provided by Microsoft at
http://www.microsoft.com/mscorp/safety/content/technologies/senderid/wizard/

I don't understand all the questions in this wizard, or know the answers
applicable to Heart's mail server (IP 79.170.40.14).  My guesswork came up
with v=spf1 mx ip4:79.170.40.52 mx:mail.fojd.org.uk +all but when I tested
this syntax using the tool at www.openspf.org I received a warning: "SPF
Ambiguity Warning: No MX records found for mx mechanism: mail.fojd.org.uk".

Can anyone advise me on this?  I spend ages just re-sending emails through
different email accounts, when really I want to send using my domain
address.

Christine Moon