Best transport from Kensington area to Watford Junction

I took the train from Euston station to Bletchley park when I visited this August, and it stopped at Watford, probably a 20 minute trip with departure and return open-ended. I took the tube from my hotel in the Bayswater neighborhood to Euston. There are probably other options but this was fast and easy--and the train was full of tour groups going to Warner Brothers.

There is an hourly train (destination sometimes Watford Junction or much more likely Milton Keynes Central) operated by Southern which calls at Shepherd's Bush train station (not to be confused with Shepherd's Bush Market tube station which serves the Hammersmith and City Line and the Circle Line or the Central Line Shepherd's Bush station, all of which are in a different place) which goes direct to Watford Junction.

It goes at various times after the hour, usually at or around xx:54 and reaches Watford Junction at around xx:21. £14.60 return train ticket, £7.30 single, so in this case no discount for a return.

But both stations are on the Oyster network and using Oyster or contactless will be cheaper than a train ticket.

Because you don't go into Zone 1 that way, so it could be a Zone 2 to Watford Junction contactless or Oyster fare of Peak: £4.70 (Monday to Friday from 0630 to 0930 and from 1600 to 1900) or Off Peak: £2.90 (At all other times including public holidays.).

But there is no free lunch is there? The down side is that that train is only hourly, and if anything comes up on the Southern network or between London and Milton Keynes that train is frequently cancelled. Check on the day if planning to use it.

Otherwise it is an easy no-change tube ride from Shepherd's Bush Market tube station on the Circle and Hammersmith and City lines to Euston Square and then a 100 metre walk into Euston train station for 5 trains an hour (2 with 3 stops to Watford Junction - destination Tring, 2 an hour non stop - destination Milton Keynes Central, and 1 express non stop - destination Northampton or Birmingham New Street). Fares will be higher but that route while slower may be easier to plan for.

Or you can take the alternate tube route to Euston from Shepherd's Bush Central line station to Oxford Circus and change to the Victoria line to Euston.