How long it takes to charge depends on what kind of power you can give to it. If you can only give a standard 16A @ 240V, it's going to take much longer (roughly 24 hours from completely empty) than if you can give it 32A 3-phase (roughly 4 hours from completely empty). Tesla has a charging calculator on its site that can help you with options and estimating. Perhaps someone from the UK can help with the most common charging options found in UK homes.
Likewise, I don't know the cost paid per kWh in the UK. At my 0.09USD price per kWh, it will cost me about $8.50 to do a complete charge from empty. Some charging rates (3 phase 32A vs. single-phase 16A, for example) are more efficient than others, and will affect that cost. The same Tesla calculator can help with cost to charge, but you'll need your per-kWh pricing.
The full-charge range of the 70D is 240 miles, I believe, which would leave your 90% charge at ~226. I have found that the rated range will reflect reality roughly around 65 mph in ~30 degree(C) weather. You'll get less range if it is colder, if it's raining, or if you are traveling at speeds greater than 70 mph.
80 miles round trip would be no problem whatsoever for a 70D.