Problems connection to PPTP Servers

[#1]

Since joining plusnet, my dad, who connects to his business VPN using PPTP has had terrible connection problems. Often timing out or not logging in at all.
I did some research. Saw thishttp://community.plus.net/forum/index.php/topic,102798.0.html earlier thread.
And also this http://wiki.aa.org.uk/index.php/TG582N#Problems_connection_to_PPTP_Servers AAISP wiki
Sadly the telnet command:
connection applist
connection unbind application PPTP port 1723
saveall
Does not help him. So i gather the problem is packet inspection and the NAT of the router. In the AAISP article it mentions the only way to resolve this is by assigning an IP block to the client, but I cannot find any information on how to do this.
It also says if you disable NAT it fixes it, but I cannot do that as many share our home internet connection.
Another option it mentioned was disabling NAT for a certain IP pool. But I am also unsure how to configure this.
Any pointers? Seems bizzare to have this problem when firewall says it allows VPN.

[#2]

Quote

AAISP article it mentions the only way to resolve this is by assigning an IP block to the client

It mentions that someone resolved an issue by doing that, however this would involve ourselves applying a block of static IPs to the account which we shouldn't need to do as this should be working with a single static IP.
I'm not aware if NAT can be disabled but let me check that with our products team here and I'll let you know.
Adam

[#3]

I don't think you can run multiple computers without a Nat. that's why it mentions the ip block, so each computer is assigned its own ip on the wan.

[#4]

Is this a grey area?
It seems a bit naughty to mention that VPN is priority traffic, mention its unblocked with standard firewall, yet there is a problem connecting via PPTP, which is probably the most common VPN connection protocol.

[#5]

Have you tried unbinding the IKE helper?
It was reported as a bug workaround for firmware R8.4.3.
connection unbind application=IKE port=500-500
saveall
http://npr.me.uk/vpnissue.html

[#6]

I run a vpn to work.  Admittedly it's router to firewall using ipsec but it's a stable as a rock when connected.  Having a few issues with the draytek 2830 keeping the vpn connected when there is no traffic over the vpn but the second there is traffic it goes rock steady.
I have never used PPTP so can't comment on it.
Before I got the 2830 I used a draytek cable router the 2910 which routed everything to the plusnet T582n, separate subnets.  I didn't expect it to work as I had to jump through many hoops with the same router from Be when getting it to work, however it worked first time.  Again vpn lan to lan from the cable router to the firewall in work using ipsec but it worked perfectly going straight through the plusnet router without a hiccup.

[#7]

Sadly the company only uses pptp.
Thanks for the link, but yes I have unbound the IKE helper it doesn't seem to make a difference.
From the client,messages appear such as "connection timed out, please check your firewall" and sometimes you can connect without a problem but it will soon throw you off. It's very intermittent.
I think ipsec works fine directly it's Hyatt pptp