Hi there Pansy.If you wait until after the summer you are going to run the risk of the pond all but drying up and that will be a far greater risk.I would have everything in place,ie a new liner,and lots of receptacles.Then on the first dull and coolish day we have that you have free,i would tackle it then.Simply remove all the water,or as much as you can and with it all the water creatures and weed that is so vital to the ponds balance.Don't worry about upsetting the fogs,toads and newts.They will hang about in the garden and return at night or when it next rains.In fact if you know rain is forecast that is an excellent time to do it as you will need a lot of water to fill it up!
Use a good quality liner,the best you can afford.When you empty out the old,as i say, get all the insect life but use the opportunity also to leave the muck that will have built up at the bottom,however you will need to sift through it over a few days to check for tadpoles,young newts etc.So save it all in a bucket or two.When you put the water back,drop in some fresh good quality soil but not any with fertiliser added.Then replant your weed and plants,and either wait for rain or use it from the tap and use a dechlorinator.
I hope that helps?I wish i could come and help.I redid mine about three years ago and was in my element up to my armpits in mud!!
