Tom310
Gathered from the forum here. Nothing the search couldn't find for you....

Simple 2.4 GHz transmitter £35

2 Gimson drives £50
2 125mm Blue wheels with inserts. £17.3

3S LiFePo4 battery £20 with P&P included.

The only expensive stuff left, the speedo's. But for less than £100 you have a unit that will be usable in combination with the Gimsons.

The rest is structural. Skip bin steel plate, Scrapyard scrounging.
Or if you can find it, a plastics working firm (sewage-system builders for example), and ask for offcuts from HDPE or PP plate.

If that ain't working. Plywood from the DIY .

of course, if you have moeny to spend there are several 1 stop shopping options. Like the robotmarketplace