I went last year. We were coming from Hackney and we ended up getting off at Earlsfield station and had a nice walk across, although if you could incorporate Southfields, then that would be nearer. We also just stopped at a small Tesco on the way for some sarnies and drinks, which I'm sure we took in with us and we grabbed a meal outside the grounds when play had finished.
I'm not sure what tickets you have, we had Court 1 tickets where the matches started at 1pm, but you can get in to the grounds as soon as they open at 10.30am and you can go to any court apart from Centre Court and Court 2 (as they are individually ticketed). Courts 3, 12 and 18 are show courts (available to ground passes) with a fair few seats, so if there was an early match on the day on those three courts that you fancied, I'd definitely try and get a seat. There were plenty of seats on Court 18 for a match we wanted to see, but ended up going for a wander and when we came back, it was absolutely packed, so we ended up going up near the balcony to watch, which was fine, but I'd rather have had a seat. Play traditionally used to start at 11.30am on the outside courts, but it has changed to 11am this year.
I'd try and get there as near to 10.30 as possible when it is much quieter (and especially the Pimms queues) as by 1ish it does massively fill up and you can be waiting in the drinks cue for a while. The programme was pretty cool as well. It cost £10 but it was A4 and had about 100 pages, so I would recommend that - a nice souvenir to take home as well.
A bit jealous that I'm not going. I applied again, but didn't get tickets and didn't fancy queuing with just going last year - I might next year if I don't get tickets again. I do however have a week off next week, so will be watching it pretty much non stop from Monday to Saturday

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Enjoy.