For unlocking for free
Just use the vodafone sim for 30 days
then go to the Vodafone website below

https://www.vodafone.co.uk/vodafone-uk/forms/unlock-code-request/

Seems OK for a budget handset - specs from GSM Arena:

Network Technology GSM / HSPA / LTE
Launch Announced 2015, September
Status Available. Released 2015, October
Body Dimensions 132.2 x 65.1 x 10 mm (5.20 x 2.56 x 0.39 in)
Weight 146 g (5.15 oz)
SIM Micro-SIM
Display Type IPS LCD capacitive touchscreen, 16M colors
Size 4.5 inches (~64.8% screen-to-body ratio)
Resolution 480 x 854 pixels (~218 ppi pixel density)
Multitouch Yes
Platform OS Android OS, v5.1 (Lollipop)
Chipset Mediatek MT6735M
CPU Quad-core 1.0 GHz Cortex-A53
GPU Mali-T720MP2
Memory Card slot microSD, up to 32 GB (dedicated slot)
Internal 8 GB, 1 GB RAM
Camera Primary 5 MP, LED flash
Features Yes
Video 720p
Secondary 2 MP
Sound Alert types Vibration; MP3, WAV ringtones
Loudspeaker Yes
3.5mm jack Yes
Comms WLAN Wi-Fi 802.11 b/g/n, hotspot
Bluetooth v4.0, A2DP
GPS Yes, with A-GPS
Radio FM radio
USB microUSB v2.0
Features Sensors Accelerometer, compass
Messaging SMS(threaded view), MMS, Email, Push Mail, IM
Browser HTML
Java No
- MP3/eAAC+ player
- MP4/H.264 player
- Document viewer
- Photo/video editor
Battery Non-removable Li-Ion 1780 mAh battery
Misc Colors Silver, Anthracite
Price group 2/10

Bought one. Looks like it can be unlocked and upgraded to Nougat pretty easily.

Haven't used an Android phone for ages so this could be a good one to have a play around with.

Cheers.

how much to unlock for giffgaff network?

Well reviewed at £50. Unlock codes look to be available to less than £2 on Ebay. Good price.

For unlocking for free
Just use the vodafone sim for 30 days
then go to the Vodafone website below

https://www.vodafone.co.uk/vodafone-uk/forms/unlock-code-request/

This is a dreadful phone. Looks good on paper, but it's *very* slow and the camera is awful. I bought one for my other half and am now looking for a replacement.

Bought this model for my daughter a while ago and she is quite happy with it, it suits all the pre-teen requirements, works with Pokemon Go and has an adequate camera, the poorest aspect of the phone is the screen, looking directly at it you are fine but the viewing angles are poor. For this price however (which is the same as I paid in Christmas 2015) it is a decent enough buy, unlocking cost me around £1.98 via ebay and was done in an hour. Just don't expect too much, it has been a reliable enough device with ok battery life, needs charging every night. I wouldn't say it is very slow at all though obviously not particularly fast compared to top of the range phones, it certainly isn't painfully slow.

Does this play Pokemon Go reasonably well? Im looking to buy one for the kids. Plus I have the older Smart First 6 which has only 512MB ram, a slower processor, smaller screen that seems resistive. Would this phone be a marked improvement over that? The Smart phone was a great emergency phone but now apps are becoming more important I think the extra ram and speed are much needed. I was wondering whether binningthe First and buying the speed is in any way sensible