Having done more online research, here is the actual Hairy Bikers recipe - but I used normal hobnobs not the chocolatey ones for the base.
This is moreish - be warned!!
Toffee Filling
115g butter
115g soft dark brown sugar
397g can sweetened condensed milk
Topping
5 ripe but firm medium bananas
450ml double cream
1 tsp fresh lemon juice
25g plain dark chocolate, coursely grated, or chocolate curls
Biscuit Base
75g butter
300g chocolate oaty biscuits (such as Hobnobs)
To make the base, melt the butter in a small pan. Break the biscuits into chunky pieces and blitz them to crumbs in a food processor. With the motor running, add the melted butter and blend until thoroughly mixed. Alternatively, put the biscuits in a strong plastic food bag and bash with a rolling pin. Tip the crumbs into a bowl and stir in the melted butter.
Tip the biscuit mixture into the centre of your tart tin and press firmly into the base and sides. Make sure the mixture is evenly distributed, especially where the base meets the sides. Chill for 30 minutes until set.
To make the toffee filling, melt the butter in a non-stick saucepan and stir in the sugar. Cook over a low heat, stirring constantly, until the sugar has dissolved and the butter and sugar look smooth with no oil floating to the surface. Add the condensed milk and bring to a gentle simmer, stirring constantly. Cook for 3 minutes, stirring, until the mixture turns a deep, creamy caramel brown. Pour the toffee gently onto the biscuit base and quickly smooth over the surface. Leave to chill for at least 1 hour and up to 8 hours before topping.
Just before serving, lightly whip the cream. It should stand in very soft peaks ? any thicker and it will look over-whipped when mixed with the bananas. Diagonally slice 4 of the bananas and scatter half of them over the toffee. Fold the rest lightly into the cream and spoon gently on top.
Slice the remaining banana and put it in a bowl with the lemon juice. Toss very gently ? this will stop the banana turning brown. Decorate the top with the lemony banana slices, poking them into the cream randomly, then sprinkle the pie with grated chocolate or decorate with chocolate curls. Serve the pie in fairly thin slices as it is very rich. (Bollocks to that bit!)