I made a mistake with the arches by accidentally purchasing five dark blue 1x6x2 arches instead of five dark blue 1x8x2 arches. This set me back about £2.50. I found four of the arches I needed on Ebay for only £3 and I bought the fifth one from Denmark along with some other pieces for my own collection.
All together the total parts cost has come to £25.23 which I think is quite a low cost considering it is a retired set but so far the pieces used are common pieces. The total postage cost was a massive £16.02 which brings the grand total to £41.25 so far.
Next time I am going to try reducing the postage cost by reducing the number of sellers I buy from. I do agree that for this part everything has not been 100% organised therefore ordering the wrong size arches. I need to pay careful attention to the required pieces next time. The next section of Market Street will be the dark blue floor and I have already ordered the parts and I have only had to make two orders so the postage will be really low! I will do a post this weekend for the next section.