Thanks all
We currently do two walks;
15mins, pavement, around block. On short lead.
40mins, mixed pavement and grass walk/play across/around field. On 5m extendible lead.
When on field she can run across grass, sniff, mooch, etc. so she is only on pavement around 10 mins
Her recall is bad at mo - too many interesting smells, etc - but have long lead to start teaching that outside.