OK, thanks first for allowing me to join the forum 
We have booked a few nights in rooms 20 minutes walk from Watford Junction, and over three days will visit the tour, and have a day in the capital. We could do with some travel advice to cover the short visit if possible.
There are 3 adults in the party, requiring off-peak fares advice, for best prices and when and how to pre-pay. (We have no Railcards or any other way of saving).
Leaving on Monday 18th September after 1pm from Preston, Lancashire.
Returning on Thursday 21st September in the afternoon sometime.
I assume the best tickets for travel there and back would be to Watford Junction Return x3. (We thought about Euston but that would mean daily travel to Watford).
Itinerary:
Monday 18th: Leave Preston, between 1pm and 3pm to arrive at the hotel (rooms in house actually) in the afternoon.
Tuesday 19th: Travel into London city for touring around the capital.
Wednesday 20th: Harry Potter World Tour (booked already).
Thursday 21st: Leave to come home (we could go back into the capital for another look around, but not guaranteed) at any time off-peak.
** On Monday 18th, we need off-peak return tickets (come home Thursday).
** On the Tuesday 19th, we need budget travel into the city - be this by train return, buses, or underground. Would it best to sort this travel on the day - because we have no fixed timescale for this days movements, but the question is which one (best value for more travel options - such as underground go anywhere all day x3, bus rambler tickets go anywhere all day x3, or mainline into Euston and wing it from there for the day!)
** On Wednesday 20th, we would walk to Watford Junction for the Harry Potter Shuttle bus service.
** On Thursday 21st we need to leave the property before 11-ish but would spend the time after that either looking around Watford, or we could go elsewhere for a few hours I suppose, as long as travel costs are cheap enough.
My daughter is paying for this (not us - i.e. mum and dad) so there is a limit to what she can afford.
To me, all that itinerary looks a touch complicated, but I guess it may be easier to plan for than I imagine.... especially with the good advice of yourselves (I was recommended this site by a friend who works for the railway somewhere).
Best regards, and thanks in advance.
Paul, Gill, and our Rachel.

We have booked a few nights in rooms 20 minutes walk from Watford Junction, and over three days will visit the tour, and have a day in the capital. We could do with some travel advice to cover the short visit if possible.
There are 3 adults in the party, requiring off-peak fares advice, for best prices and when and how to pre-pay. (We have no Railcards or any other way of saving).
Leaving on Monday 18th September after 1pm from Preston, Lancashire.
Returning on Thursday 21st September in the afternoon sometime.
I assume the best tickets for travel there and back would be to Watford Junction Return x3. (We thought about Euston but that would mean daily travel to Watford).
Itinerary:
Monday 18th: Leave Preston, between 1pm and 3pm to arrive at the hotel (rooms in house actually) in the afternoon.
Tuesday 19th: Travel into London city for touring around the capital.
Wednesday 20th: Harry Potter World Tour (booked already).
Thursday 21st: Leave to come home (we could go back into the capital for another look around, but not guaranteed) at any time off-peak.
** On Monday 18th, we need off-peak return tickets (come home Thursday).
** On the Tuesday 19th, we need budget travel into the city - be this by train return, buses, or underground. Would it best to sort this travel on the day - because we have no fixed timescale for this days movements, but the question is which one (best value for more travel options - such as underground go anywhere all day x3, bus rambler tickets go anywhere all day x3, or mainline into Euston and wing it from there for the day!)
** On Wednesday 20th, we would walk to Watford Junction for the Harry Potter Shuttle bus service.
** On Thursday 21st we need to leave the property before 11-ish but would spend the time after that either looking around Watford, or we could go elsewhere for a few hours I suppose, as long as travel costs are cheap enough.
My daughter is paying for this (not us - i.e. mum and dad) so there is a limit to what she can afford.
To me, all that itinerary looks a touch complicated, but I guess it may be easier to plan for than I imagine.... especially with the good advice of yourselves (I was recommended this site by a friend who works for the railway somewhere).
Best regards, and thanks in advance.
Paul, Gill, and our Rachel.