Text is genuinely mobile, messenger doesn't cut it as the other end is going to be fixed location unless Rizza is on a 3G contract and has yahoo on her phone.
I have lost track of the money we have wasted on txt, I got it under control this year when I bought the device I posted about in the link below.
http://filipinaroses.com/showthread.php?t=18482
Now that Ana is back in Manila it's costs us 1 peso each way indeed Ana has so many free txt now that we wont have to buy load at either end for another 2 months.
Text from Phils to UK are 20 peso each, UK to Phils as you say 10p I guess you are with O2?
When Ana was in Korea my international txt messages were included in my Flext allowance effectively free as were about 200 minutes of calls a month. Now that she is back in the Phils my T-mobile contract does not cover the calls or txt, so it's 17p a txt and £1.11 a minute calls. :(
A Skype to Go number in the UK will let you call from your mobile to a local number (free in your contract) then you just pay Skype about 14p a minute for the call to a Philippine mobile and 10p a minute to a landline.
Skype to Skype is obviously best (free + video call) .
The Smart Plug n Talk is a godsend still not truly flexible but I have a computer just about anywhere I go.
Hope this is helpful to you Northerner!
Oh almost forgot Skype txt messages are 3.5p to the Phils but the reply number will be expensive for Rizza as it will be your UK cellphone number.
Jim