Here’s a funny thing: it costs a lot less to get a day return train ticket from the south coast to London than the other way round – about £10 less for non railcard holders. Buy on-line to take advantage! But cheapest of all is to get a Thameslink only ticket (either direction). You’d have to get a Thameslink train from St. Pancras, Blackfriars, London Bridge or East Croydon to Three Bridges (see below!), and back. Saves nearly £17 for non railcard holders!
Your match ticket at Brighton covers free use of buses and trains to and from the stadium from Hayward’s Heath in the north, Worthing in the west and Eastbourne in the east – applies from 11:30 to 21:00. Trouble is, for 30/3/19 there are no trains to Brighton and Lewes after Three Bridges. Replacement buses to Brighton should run every 10 minutes and take 45 minutes. It’s also supposed to be a 45 minute run to Lewes (every 30 mins), which has a more pleasant connection to Falmer for the Amex. DON’T BE TEMPTED TO GET ON AN ALL STATIONS STOPPING BUS SERVICE!
An alternative is the train service from London to Brighton via Littlehampton – look at a map to see why this is a bad idea. But the route does give the opportunity to enjoy The Green Man Ale & Cider House (West Worthing), Booksteed Ale House (Worthing), Stanley Ale House (Lancing), Buckingham Arms (Shoreham), Watchmaker’s Arms (Hove) and Evening Star (Brighton) – all within 100 yards of the stations.
Obviously you use the approach from the west if travelling from Southampton. Note that Southampton to Lewes costs the same as to Brighton and stopping en route could find you stuck in the queuing system to get the train from Brighton to Falmer. You’ll also hit it trying to get back on the Coastway West route on the return journey. And heaven knows what chaos could ensue for the replacement buses back to ‘Bridges.
By car, Brighton, Hove and Lewes are notoriously difficult for parking and you might consider one of BHA’s Park & Ride options. There’s a small Pay & Display car park at Lewes FC which is next to Lewes station, and there is free street parking north of West Worthing, Worthing or Shoreham stations, near the pubs above.
By the way, BHA don’t allow flasks or large bags to be taken into the stadium and Sussex police can and frequently do arrest people for homophobic abuse.