No, we are not a garage and do not have facilities to undertake this work.
You need to lookup a local EV garage to see if they can help. Look on HEVRA - Hybrid and Electric Vehicle Repair Alliance. HEVRA members are garages that have been checked for the right qualifications, tools and equipment to service and repair electric and hybrid vehicles - https://www.hevra.org.uk/
We can supply the batteries if they are in the range we sell.
For Nissan Leaf 40kWh upgrades talk to Matt at Cedar Garage 01903 248 967 based in Worthing. Please do mention you got you number from Second Life EV Batteries.