REALLY confused with DNS Issues

[#1]

Im after some info with regard to DNS.
I have a domain name currently hosted with 123 Reg which I would like to move to PAYH.
I would like to ONLY move the hosting and leave everything else where it is.
I've spoken with PAYH support and both 123 Reg support and got conflicting advice.
PAYH Support recommend:
In 123 Reg Control Panel Set:
mydomain.co.uk  A  212.56.83.199
www.mydomain.co.uk CNAME mydomain.co.uk
ftp.mydomain.co.uk CNAME mydomain.co.uk
Now, 123 Reg support have recommended to only add the following:
WWW CNAME mydomain.co.uk
Now, earlier on, I had both in and for the first time it all worked (even though these things take up to 24 hours), but now its not working.
I would like to be able to modify this tonight and leave it to propigate knowing full well that ive entered 100% the correct items.

Can anyone shed any light on what should Exactly be in the123 reg control panel, in simple terms?
In addition to the above, there is also:
@  A 194.154.164.82
Kev, If you happen to read this, sorry but I get easily confused!
Adam

[#2]

I would like to do the same with plusnet hosting and externally bought domain name if this is possible (I use google apps for other stuff on the domain including email)

[#3]

Have you set up an alias on PAYH?
I don't use 123-reg, but the @ record should relate to the domain itself: yourdomain.co.uk. You would need to change 194.154.164.82 to 212.56.83.199 to point it to PAYH and then the alias on PAYH will route it at that end.
You would then need to point the subdomain www, either at the domain (using CNAME) or at PAYH: www  A  212.56.83.199
Then wait for it to propagate.
Good luck.
Gabe