Good luck with the challenge. A colleague and I attempted to fly to Ireland from the edge of the London CTR back in the early 2000's using a 300,000 cubic foot balloon. We could find no record of a westbound crossing so it was to be an aviation "first". The fuel consumption was higher than expected and we hit severe turbulence over the Welsh mountains causing us to climb and swing right. With our fuel state now doubtful and a projected arrival into the Dublin airspace, we landed (at speed) on a Welsh coastal farm.
We knew it was risky but we planned for every eventuality, including "borrowing" (cough cough) survival gear from Auntie Betty, which was returned and was never missed. It was great fun, all the way from planning with a map laid out on the floor of a Henley curry house to stopping at a favourite Wiltshire pub on the way home for a slap up dinner with the retrieve crew.
I would do it all again, even the small airspace infringement that didn't happen.....honest. Are you planning to dump your empty tanks as you go or take them all the way ? We scrounged our extra tanks and mounted the least valuable on the outside of the basket so they could be jettisoned if needed. The posh titanium tanks were in the centre of the basket for protection. A 50p sheet of orange stickers was handy for marking each empty tank so at a glance, we knew our fuel state.
Don't get your feet wet !