However - look at the costs/benefits of your options:
- Cost of getting a new phone, which will not only solve your sat nav problems but will replace your current glitchy old model, with the best swiss-army knife you can possibly own: £55 (See >here<.)
- Cost of replacing your sat nav battery (which may, or may not, fix your problem. Plus you'll have to fit it.): Around £20. See >here<, although I couldn't find one for your model.)
- Cost of a new sat nav: £60. (The cheapest in Argos.)
- There are plenty of cheap phone contracts with data. For £6, GiffGaff gives you 300 mins talk, 500 texts and 500MB data - which is more than I ever use in a month of heavy use, including sat nav. You would keep your current number.
- As mentioned above, you don't necessarily need data to run a phone sat nav - there are plenty of free off-line versions. (I use one called 'HERE we go', which was previously known as Nokia Maps.)
I will now shut up on the matter - I can imagine this thread is making you feel the same as I do when the internet tells me I must throw my indies away and buy a manifolded twinset or a rebreather...