Grandstream HT801 - international dialling prefix in CLID

[g7omn]

I have a Grandstream HT801 ATA successfully working with Vodafone VOIP on a draytek 2862, with a Siemens SL795 Dect phone attached to the HT801

I have a little annoyance (because my wife can't get her head around this), that the HT801 passes all the international dialling prefixes on in CLID, so any UK based number is prefixed with +44 or 0044 (If I set Replace Beginning '+' with 00 in Caller ID to yes) and i can see this from the CDR file preview.
Is there a way to substitute the international prefixes for a simple 0 for a call received from the UK?
Oddly, if i connect an old Betacomm phone that supports CLID - that doesn't decode the CLID at all, so I wonder if i have a setting incorrect?

Caller ID fetch order is Auto

SLIC Setting = BT

Caller ID scheme = SIN 227 - BT

DTMF Caller ID  start and stop tones are "default."

Disable unknown caller ID = No

Replace Beginning '+' with 00 in Caller ID - I have tried yes and no

Number of digits to strip from caller ID = 0

[Ripshod]

Try:

Replace Beginning '+' with 00 in Caller ID - yes

Number of digits to strip from caller ID = 1

See how that goes

[g7omn]

I worked out why the betacom phone wouldn't work for displaying CLID - it needed 30mA OnHook DC Feed Current.

So I have tried:

Replace Beginning '+' with 00 in Caller ID set to yes - this succesfully inserts a 00 (without it neither of the phones display a +, which is kind of expected, as I don't traditional phones from when CLID was invented wouldn't have been capable of displaying. a +
Number of digits to strip from caller ID:

"1" strips out the 00 (so probably stripping the +) and just displays the country code and then the calling number

2 strips the first digit of the country code

3 strips out the second digit as expected.
Physically stripping digits unselectively is problematic, as you would want to know correctly for any international calls (given that +1 is USA), really stripping multiple digits is a no-no.

Really it needs a substitution rule  to replace +44 with 0 - but i can't see anywhere to configure that.
I can't remember if the V/F router deals with it properly or not, if it doesn't it's probably a v/f config?
I'd be interested to see if anyone else with HT801's sees the same.

[Ripshod]

Yeah it looks like those are the only two relevant settings on the HT801. It's been a while though so I could be wrong.