Navionics Silver charts are often bundled. They only have data out to the 10m line - not much use if you're fishing!
I used to preach that bigger is better with plotters. That extra screen size is great but always comes at a price. Now a lot of the plotter systems come with WIFI so you can relay the data to a tablet and often control the plotter FROM the tablet as well. Maybe one to consider if you just need basic functions but want a big screen for fishing/nav. planning.
There are plotter/sounder combos (which you want) out there with WIFI and silver charts for around the £250 mark. Charts can be upgraded (maybe your local area only?) later for a modest cost