There's no single right answer, just a trade-off between cost and effort.
A free spot like your home or a park saves on hire, but you become the set-up crew, weather contingency and clean-up team. Parks also come with rules. Data from
The Royal Parks shows that groups of up to 30 can hold an informal rugs-on-the-ground picnic with no permit or notice, though tables, chairs, gazebos and BBQs aren't allowed and you can't reserve an area exclusively. Groups of 31 to 100 need advance approval. If you want the open-air feel without the red tape, check out
outdoor party venues in Shoreditch.
Hiring a park isn't always cheap or quick either. The
Royal Borough of Kensington and Chelsea asks for at least six weeks' notice for a small park event and charges private-hire fees that start around £236 for a half day, plus an administration fee and a refundable deposit. Rules vary from borough to borough, and some restrict private parties altogether. Insurance matters too.
Tickts explains that public liability cover isn't legally required for a private organiser, but most venues and councils expect proof, commonly £1 to 2 million for smaller indoor events, so check with a specialist broker. A hired venue costs more upfront, but bundles amenities, staff, insurance and far less hassle, and you can browse
London venues with a patio for that outdoor mood without the setup. Event host Kate Pauley reckons a hired venue wins nine times out of ten, since it comes with insurance, a bigger kitchen and no clean-up landing on you.
Pro tip: Include setup and clearing up in the booked hours, and ask the host which facilities and outdoor areas are reserved for your group.